Hi Jeremy,
I have made several changes;

There are 2 ‘RadioButtons':
‘Use Current Printer Settings’ – Select this one and no printer settings will be changed
‘Modify Printer Settings’ – Select this one and selections in the ‘GroupBox’ will be appied.

Inside the ‘GroupBox’;
Select the ‘RadioButton’ to the left of the Computer Lab Printer and it will be set as the default printer.

Select the ‘RadioButton’ to the left of the Library Printer and it will be set as the default printer.

Place a check next to each printer you want to install.

Click the ‘Click Here To Close This Window’ and the chosen printer settings will be applied.

Here is your modified code:
Code:

Break On
$System = CreateObject("Kixtart.System")
If Not $System
$nul= MessageBox("KiXforms Not Initiated. This Script Will Now Close.","Error",16)
Quit()
EndIf

$Form = $System.Form()
$Form.Text = "St. Matthew School Computer Network - Admin Site Printer Install"
$Form.Width = 600
$Form.Height = 600
$Form.BackColor = $Form.RGB(255,255,0)

$Panel = $Form.Controls.Add("Panel")
$Panel.Dock = "top" ;resize for your needs
$Panel.BackgroundImage = "\\s096-a0290-01\sch030$\printers\matthew.jpg"

$Instructions = $Form.Controls.Add("Label")
$Instructions.Height = 31
$Instructions.Left = 10
$Instructions.TextAlign = 32 ;Center Text in Label
$Instructions.Text = "Please wait while I determine which printers you are already connected to..."
$Instructions.Top = 135
$Instructions.Width = $Form.ClientWidth-20

$Listbox = $Form.Controls.Add("Listbox")
$Listbox.Height = 150
$Listbox.Left = 280
$Listbox.Top = 175
$Listbox.Width = 250

$DefPrintersRadioButton = $Form.Controls.Add("RadioButton")
$DefPrintersRadioButton.Left = 10
$DefPrintersRadioButton.Top = $Listbox.Bottom+10
$DefPrintersRadioButton.Text = "Use Current Printer Settings"
$DefPrintersRadioButton.Width = 150
$DefPrintersRadioButton.Checked = "True"
$DefPrintersRadioButton.OnClick = "CheckPrinterRadioButtons()"

$ModPrintersRadioButton = $Form.Controls.Add("RadioButton")
$ModPrintersRadioButton.Left = 10
$ModPrintersRadioButton.Top = $DefPrintersRadioButton.Bottom+10
$ModPrintersRadioButton.Text = "Modify Printer Settings"
$ModPrintersRadioButton.Width = 150
$ModPrintersRadioButton.OnClick = "CheckPrinterRadioButtons()"

$PrintersGroupBox = $Form.Controls.Add("GroupBox")
$PrintersGroupBox.Left = $ModPrintersRadioButton.Right+10
$PrintersGroupBox.Top = $ModPrintersRadioButton.Top
$PrintersGroupBox.Height = 85
$PrintersGroupBox.Width = $Form.ClientWidth-180
$PrintersGroupBox.Text = "Default Install Printer"

$ComputerLabRadioButton = $PrintersGroupBox.Controls.Add("RadioButton")
$ComputerLabRadioButton.Left = 20
$ComputerLabRadioButton.Top = 20
$ComputerLabRadioButton.Height = 20
$ComputerLabRadioButton.Width = 20
$ComputerLabRadioButton.Enabled = "False"
$ComputerLabRadioButton.OnClick = "CheckComputerLabRadioButton()"

$ComputerLabCheckBox = $PrintersGroupBox.Controls.Add("CheckBox")
$ComputerLabCheckBox.Left = $ComputerLabRadioButton.Right+20
$ComputerLabCheckBox.Top = $ComputerLabRadioButton.Top
$ComputerLabCheckBox.Height = 20
$ComputerLabCheckBox.Width = $PrintersGroupBox.Width-$ComputerLabCheckBox.Left-10
$ComputerLabCheckBox.Text = "Computer Lab Printer"
$ComputerLabCheckBox.Enabled = "False"
$ComputerLabCheckBox.OnClick = "CheckComputerLabCheckBox()"

$LibraryPrinterRadioButton = $PrintersGroupBox.Controls.Add("RadioButton")
$LibraryPrinterRadioButton.Left = 20
$LibraryPrinterRadioButton.Top = $ComputerLabRadioButton.Bottom
$LibraryPrinterRadioButton.Height = 20
$LibraryPrinterRadioButton.Width = 20
$LibraryPrinterRadioButton.Enabled = "False"
$LibraryPrinterRadioButton.OnClick = "CheckLibraryPrinterRadioButton()"

$LibraryPrinterCheckBox = $PrintersGroupBox.Controls.Add("CheckBox")
$LibraryPrinterCheckBox.Left = $LibraryPrinterRadioButton.Right+20
$LibraryPrinterCheckBox.Top = $LibraryPrinterRadioButton.Top
$LibraryPrinterCheckBox.Height = 20
$LibraryPrinterCheckBox.Width = $PrintersGroupBox.Width-$LibraryPrinterCheckBox.Left-10
$LibraryPrinterCheckBox.Text = "Library Printer"
$LibraryPrinterCheckBox.Enabled = "False"
$LibraryPrinterCheckBox.OnClick = "CheckLibraryPrinterCheckBox()"

$OfficePrinterCheckBox = $PrintersGroupBox.Controls.Add("CheckBox")
$OfficePrinterCheckBox.Left = $LibraryPrinterRadioButton.Right+20
$OfficePrinterCheckBox.Top = $LibraryPrinterCheckBox.Bottom
$OfficePrinterCheckBox.Height = 20
$OfficePrinterCheckBox.Width = $PrintersGroupBox.Width-$OfficePrinterCheckBox.Left-10
$OfficePrinterCheckBox.Text = "Office Printer"
$OfficePrinterCheckBox.Enabled = "False"

$Exit = $Form.Controls.Add("Button")
$Exit.Cancel = "True"
$Exit.Default = "True"
$Exit.Height = 31
$Exit.Left = 10
$Exit.Text = "Click Here To Close This Window"
$Exit.Top = $PrintersGroupBox.Bottom+10
$Exit.Width = $Form.ClientWidth-20
$Exit.OnClick = "ExitButton()"

$Form.Center
$Form.Show

GetDefaultPrinter()
EnumPrinters()

While $Form.Visible
$nul = Execute($Form.DoEvents)
Loop
Exit 1

Function GetDefaultPrinter()

;FUNCTION GetDefaultPrinter()
;
;AUTHOR Jochen Polster (jochenDOTpolsterATgmxDOTnet)
;
;VERSION 1.0
;
;VERSION HISTORY 1.0 2004/04/28 Initial release
;
;ACTION Retrieves the current default Printer
;
;SYNTAX GetDefaultPrinter()
;
;PARAMETERS none
;
;REMARKS won't work with 9x OS
;
;RETURNS The current Users default Printer
;
;DEPENDENCIES None !
;
;EXAMPLES $default = GetDefaultPrinter

$GetDefaultPrinter = Join(Split(ReadValue("HKEY_USERS\"+@sid+"\Software\Microsoft\Windows NT\CurrentVersion\Windows","Device"),',',1),'')
$Listbox2.additem("Default Printer = "+$GetDefaultPrinter)
;Create blank space between default printer listing and the listing of all printers.
$Listbox2.additem("")

EndFunction

Function EnumPrinters()

;Writes all printer to a file.
;$array=printerlist()
;$rc = Open (1, "c:\installedprinters.txt", 5)
;For Each $printer in $array
; $rc = WriteLine (1, $printer + " is installed on: " + @WKSTA + @CRLF)
;Next
;$rc = Close(1)

;DISPLAY LOCAL AND NETWORKED PRINTERS

;shows the printers on your screen.
$array=printerlist()
For Each $printer in $array
$Listbox2.additem("Printer = "+$printer)
Next

EndFunction

Function PrinterList(optional $remotepc, optional $displaymode)

;Function:
; PrinterList()
;
;Author:
; Allen Powell (Al_Po)
;
;Version:
; 1.3.1 (2006/05/10 fixed error detecting Print Servers sharing IP Printers)
;
;Revisions
; 1.3.0 (2005/10/21 added options to distinguish local or remote printers)
; 1.2.0 (2005/07/19 optimized code)
; 1.1.0 (2004/08/09 undimmed variable fix)
; 1.0.0 (2003/06/26 Original)
;
;Action:
; Creates an array/list of Printers, and optionally their ports installed, on a local or remote computer.&n bsp;
;
;Syntax:
; Printerlist(optional $remotepc,optional $displaymode)
;
;Parameters:
; $RemotePC: (Optional)
; Remote Computer. If omitted defaults to localpc.
; $DisplayMode (Optional)
; 0 - show all printers, don't display port info (Default)
; 1 - show all printers, display port info
; 2 - show local printers, don't display port info
; 3 - show local printers, display port info
; 4 - show remote printers, don't display port info
; 5 - show remote printers, display port info
;Returns:
; Array of Printers
;
;Dependencies:
; WMI
;
;Example:
;
;break on
;$RC=Setoption("WrapAtEOL","on")
;
;$array=printerlist()
;for each $printer in $array
; ? $printer
;next
;
;Source:
Dim $service,$printer,$printers,$printerdesc[0],$counter,$portname,$printername
If $remotepc=""
$remotepc="."
EndIf
$Service = GetObject("winmgmts:\\" + $remotepc + "\root\cimv2")
If @error
Exit @error
EndIf
$Printers=$service.execquery ('select * from Win32_Printer')
For Each $printer in $printers
ReDim preserve $printerdesc[$counter]
If $displaymode & 1
$portname = "," + $printer.portname
EndIf
Select
Case $displaymode & 4 ;remote printers
If Left($printer.portname,2)="\\" Or Left($printer.name,2)=="\\"
$printername=$printer.name
EndIf
Case $displaymode & 2 ;local printers
If Left($printer.portname,2)<>"\\" And Left($printer.name,2)<>"\\"
$printername=$printer.name
EndIf
Case 1 ; all printers
$printername=$printer.name
EndSelect
If $printername<>""
$printerdesc[$counter]=$printername + $portname
$counter=$counter + 1
$printername=""
EndIf
Next
$PrinterList=$printerdesc

EndFunction

Function ExitButton()
SelectAPrinter()
Quit()
EndFunction

Function AddPrinter($Port,$PrinterType,optional $DriverInf,optional $PrinterDesc,optional $remotepc,optional $Default)
;Function:
; AddPrinter()
;
;Author:
; Allen Powell (Al_Po)
;
;Version:
; 1.0
;
;Action:
; Add IP,LPT, Or COM Printers locally Or remotely. Also, add PrintServer connections locally.
;
;Syntax:
; AddPrinter($Port,$PrinterType,optional $DriverInf,optional $PrinterDesc,optional $remotepc,optional $Default)
;
;Parameters:
; $Port: (required)
; IPAddress (xxx.xxx.xxx.xxx)
; LPT (LPT1:)
; COM (COM1:)
; PrintServer (\\server\printer)
; $PrinterType: (required)
; Descriptor of Printer within INF file
; Note: If using a PrintServer, $PrinterType value is ignored.
; $DriverInf: (Optional)
; Location And name of INF file containing print drivers
; Note: If omitted, attempts to Use default Windows Print Drivers
; $PrinterDesc: (Optional)
; Description of Printer
; Note: If ommitted, $PrinterDesc = PrinterType
; $RemotePC: (Optional)
; PC to install Printer/Drivers on. If omitted defaults to localpc.
; Note: Ignored If $Port is a PrintServer
; $Default: (Optional)
; 0 = Do Not Set as Default Printer (Default)
; 1 = Set as Default Printer
;
;Returns:
; 1 - Successful
; 0 - Failed
; If Failed sets @error to
; -4 - Error connecting to RemotePC
; -3 - Could Not Open/find INF file
; -2 - Could Not find $PrinterType in INF file
; -1 - Unrecognized Port
;
;Dependencies:
; Windows 2000 Professional And up
; rundll32 printui.dll,PrintUIEntry
;
;Examples:
;$=AddPrinter("192.168.1.1","Xerox DocumentCenter 555 PCL6","\\Server\PrinterDrives\Xerox\dc555pcl\dc555x.inf","Xerox Document Centre 55 5 PCL6 in Office",REMOTEPC,1)
;$=Addprinter("LPT1","HP LaserJet 8100 Series PS",,"HP8100 in IS(test)")
;$=AddPrinter("192.168.1.1","HP LaserJet 8100 Series PS",,"HP8100 in IS(test)",,1)
;$=AddPrinter('\\server\printer','_')
;Source:

Dim $quitloop,$IPPrinterKey,$PrinterCMD
$AddPrinter=0
If Not Left($Port,2)="\\"
If $Driverinf=""
$DriverInf="%windir%\inf\ntprint.inf"
EndIf
If Not Exist($DriverInf)
Exit -3
EndIf
Shell '%comspec% /c type "$driverinf">%temp%\addprinter.txt'
If Open(3,"%temp%\addprinter.txt",0)=0
$quitloop=0
While @error=0 And $quitloop=0
$line=ReadLine(3)
$quitloop=InStr($line,$PrinterType)
Loop
$=Close(3)
If $quitloop=0
Exit -2
EndIf
Else
Exit -3
EndIf
EndIf
If $PrinterDesc=""
$PrinterDesc=$PrinterType
EndIf
If $remotepc=""
$remotepc='\\'+ @wksta
Else
If Not Left($remotepc,2)="\\"
$remotepc='\\' + $remotepc
EndIf
EndIf

Select
Case Left($Port,2)="\\"
$printserver=1
$printerdesc=$port
Case InStr($Port,".")
$IPPrinterKey = '$remotepc\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Print\Monitors\Standard TCP/IP Port\Ports\IP_' +$Port
If Not KeyExist($IPPrinterKey)
$=AddKey($IPPrinterKey)
$=WriteValue($IPPrinterKey,"Protocol","00000001","REG_DWORD")
$=WriteValue($IPPrinterKey,"Version","00000001","REG_DWORD")
$=WriteValue($IPPrinterKey,"HostName","", "REG_SZ")
$=WriteValue($IPPrinterKey,"IPAddress","$Port","REG_SZ")
$=WriteValue($IPPrinterKey,"HWAddress","","REG_SZ")
$=WriteValue($IPPrinterKey,"PortNumber","00009100","REG_DWORD")
$=WriteValue($IPPrinterKey,"SNMP Community","public","REG_SZ")
$=WriteValue($IPPrinterKey,"SNMP Enabled","00000001","REG_DWORD")
$=WriteValue($IPPrinterKey,"SNMP Index","00000001","REG_DWORD")
EndIf
$objects=GetObject("winmgmts:{impersonationLevel=impersonate}!"+$remotepc+"\root\cimv2")
If Not @error=0
Exit -4
EndIf
$services=$objects.ExecQuery('Select * from Win32_Service WHERE Name = "Spooler"')
For Each $spooler in $services
$=Execute('$$=$$spooler.stopservice()')
Next
Sleep 1
For Each $spooler in $services
$=Execute('$$=$$spooler.startservice()')
Next
$port='IP_$port'
Case UCase(Left($Port,3))="LPT" Or UCase(Left($Port,3))="COM"
If Not Right($port,1)=":"
$Port=$port+":"
EndIf
If Not Val(Left(Right($port,2),1))>=1
Exit -1
EndIf
Case UCase(Left($Port,4))="FILE"
If Not Right($port,1)=":"
$Port=$port+":"
EndIf
Case 1
Exit -1
EndSelect
If Not $Printserver=1
$printercmd='rundll32 printui.dll,PrintUIEntry /if /b "$printerdesc" /c "$remotepc" ' +
'/f "$driverinf" /r "$port" /m "$Printertype" /z /u '
Shell $printercmd
Else
If Not AddPrinterConnection($port)=0
Exit @error
EndIf
EndIf
If $default=1
If Not SetDefaultPrinter($PrinterDesc)=0
Exit @error
EndIf
EndIf
$AddPrinter=1
EndFunction

Function SelectAPrinter()

If $ModPrintersRadioButton.Checked = "True"
Select
Case ($LibraryPrinterRadioButton.Checked = "False") And ($LibraryPrinterCheckBox.CheckState = -1)
AddPrinter("10.48.18.1","Lexmark T640","\\s096-a290-01\sch030$\printers\t640.inf","Library Printer",0)
Case ($LibraryPrinterRadioButton.Checked = "True") And ($LibraryPrinterCheckBox.CheckState = -1)
AddPrinter("10.48.18.1","Lexmark T640","\\s096-a290-01\sch030$\printers\t640.inf","Library Printer",1)
Case ($ComputerLabRadioButton.Checked = "False") And ($ComputerLabCheckBox.CheckState = -1)
AddPrinter("10.48.18.2","Lexmark T640","\\s096-a290-01\sch030$\printers\t640.inf","Computer Lab Printer",0)
Case ($ComputerLabRadioButton.Checked = "True") And ($ComputerLabCheckBox.CheckState = -1)
AddPrinter("10.48.18.2","Lexmark T640","\\s096-a290-01\sch030$\printers\t640.inf","Computer Lab Printer",1)
Case $OfficePrinterCheckBox.CheckState = -1
AddPrinter("10.48.18.3","Lexmark T640","\\s096-a290-01\sch030$\printers\t640.inf","Office Printer",0)
EndSelect
EndIf

EndFunction

Function CheckPrinterRadioButtons()

If $DefPrintersRadioButton.Checked = "True"
$ComputerLabRadioButton.Enabled = "True"
$LibraryPrinterRadioButton.Enabled = "True"
$ComputerLabCheckBox.Enabled = "True"
$LibraryPrinterCheckBox.Enabled = "True"
$OfficePrinterCheckBox.Enabled = "True"

$ComputerLabRadioButton.Checked = "True"
Else
$ComputerLabRadioButton.Enabled = "False"
$LibraryPrinterRadioButton.Enabled = "False"
$ComputerLabCheckBox.Enabled = "False"
$LibraryPrinterCheckBox.Enabled = "False"
$OfficePrinterCheckBox.Enabled = "False"

$ComputerLabRadioButton.Checked = "False"
$LibraryPrinterRadioButton.Checked = "False"

$ComputerLabCheckBox.CheckState = 0
$LibraryPrinterCheckBox.CheckState = 0
$OfficePrinterCheckBox.CheckState = 0
EndIf

EndFunction

Function CheckComputerLabRadioButton()

$LibraryPrinterRadioButton.Checked = "False"
$ComputerLabCheckBox.Checked = "True"

EndFunction

Function CheckLibraryPrinterRadioButton()

$ComputerLabRadioButton.Checked = "False"
$LibraryPrinterCheckBox.Checked = "True"

EndFunction

Function CheckComputerLabCheckBox()

If $LibraryPrinterRadioButton.Checked = "True"
$ComputerLabCheckBox.Checked = "True"
EndIf

EndFunction

Function CheckLibraryPrinterCheckBox()

If $ComputerLabRadioButton.Checked = "True"
$LibraryPrinterCheckBox.Checked = "True"
EndIf

EndFunction

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