Why not just add another select at the begging? Such as:

 Code:
$computerprt = left (@wksta, 6)
select
;Xen systems
case left(@wksta, 6) = "xendes"
AddPrinterConnection ("\\printserver\printerxen")
SetDefaultPrinter("\\printserver\printerxen")
;Locatie 1
case $computerprt = "LA-MAN"
AddPrinterConnection ("\\printserver\printer1")
SetDefaultPrinter("\\printserver\printer1")
;Locatie 2
case $computerprt = "CA-DOC"
AddPrinterConnection ("\\printserver\printer2")
SetDefaultPrinter("\\printserver\printer2")
endselect