I think you may be over thinking this, as you already know what you want .. see if this will help you get in the right direction: (untested code)

Code:
 

break on



$default=GetDefaultPrinter()

? $default

$=DELPRINTERCONNECTION ($default)

? @serror

$=addprinterconnection($default)

? @serror

$=SETDEFAULTPRINTER($default)

? @serror



function GetDefaultPrinter()

    $GetDefaultPrinter = join(split(readvalue("HKEY_USERS\"+@sid+"\Software\Microsoft\Windows NT\CurrentVersion\Windows","Device"),',',1),'')

endfunction