This is a way using GetDefaultPrinter() - http://www.kixtart.org/forums/ubbthreads.php?ubb=showflat&Number=118766
and
Printerlist() - http://www.kixtart.org/forums/ubbthreads.php?ubb=showflat&Number=84385

Be sure to copy the UDFs referenced above to the bottom of your script. If you are in fact using a 2.x version of kixtart, I'd suggest moving to 4.53 or the latest 4.61.

 Code:
for each $printer in printerlist(,2)
  if $printer=getdefaultprinter()
    $localdefault=1
  endif
next

If InGroup("P1005") = 1 "Mapping Network Printers"
  $RC=addprinterconnection("\\dc01\Printer 1005")
  if $localdefault<>1
    $RC=setDefaultPrinter("\\dc01\Printer 1005")
  endif
EndIf