Ryan,

Supplied code by Bryce worked for me too. Here is a minor revision. Make sure you're running KiXtart 4.22

Code:
Break On
Dim $SO
$SO=SetOption('Explicit','On')
$SO=SetOption('NoVarsInStrings','On')
 
Dim $DomainGroups[0],$grouptoadd,$Obj,$GroupObj,$i
 
$grouptoadd = @DOMAIN + "\DomainGroupYouWantToCheckFor"
 
$Obj = GetObject("WinNT://" + @WKSTA + "/Administrators")
$Obj.filter = "group",""
For Each $GroupObj In $Obj.Members
  If Split($groupobj.adspath,"/")[3] <> @WKSTA
    $DomainGroups[$i] = Split($groupobj.adspath,"/")[2] +"\" + Split($groupobj.adspath,"/")[3]
    $i = $i + 1
    ReDim Preserve $DomainGroups[$i]
  EndIf
Next
 
If AScan($DomainGroups,$GroupToAdd) = -1
  $groupToAdd + " was not found in " + $obj.adspath ?
Else
  $groupToAdd + " was found in " + $obj.adspath ?
EndIf


 
This code should enumerate the current accounts and groups on the system.

Code:
Break On
Dim $SO
$SO=SetOption('Explicit','On')
$SO=SetOption('NoVarsInStrings','On')
 
EnumLocalGroups(@DOMAIN,@WKSTA)
 
Function EnumLocalGroups($Domain,$System)
  Dim $Array,$colGroups,$objGroup,$objUser,$Flag
  $Array = "group",""
  $colGroups = GetObject("WinNT://" + $Domain + '/' + $System )
  $colGroups.Filter = $Array
  $System ?
  For Each $objGroup In $colGroups
    $objGroup.Name ?
    For Each $objUser in $objGroup.Members
      CHR(9) + $objUser.Name ?
    Next
  Next
EndFunction


Then code like this should be able to add to the group if you already have Admin rights on the system.

Code:
Break On
Dim $SO,$AddAdmin
$SO=SetOption('Explicit','On')
$SO=SetOption('NoVarsInStrings','On')
 
$AddAdmin = AddToLocalAdmin('computer to add to','Administrators','some domain','some group')
 
Function AddToLocalAdmin($Computer,$GroupToAddTo,$Domain,optional $GroupToAdd,optional $AccountToAdd)
  Dim $Group,$User,$Admin,$Err
  $Group   = GetObject('WinNT://' + $Computer +  '/' + $GroupToAddTo + ',group')
  If $GroupToAdd<>""
    $User  = GetObject('WinNT://' + $Domain + '/' + $GroupToAdd + ',group')
  EndIf
  If $AccountToAdd<>""
    $User  = GetObject('WinNT://' + $Domain + '/' + $AccountToAdd + ',user')
  EndIf
  $Group.Add($User.ADsPath)
  $Err = @ERROR
  $AddToLocalAdmin=$Err
EndFunction
 
Function fnCOMErr($lErr)
  If $lErr<0 $lErr=VAL("&"+Right(DecToHex($lErr),4)) EndIf
  Exit $lErr
Endfunction