We decided to go with a little program called "ntname.exe". It returns the logged in workstation for any given username. If the username is not logged in you get back nothing. Easy enough! Only problem is people who are smart enough to unplug their network cable wile logging in on a second PC, but I don't see that solved by this script...

code:

IF INGROUP("MULTIPLE") GOTO NANTNAME ENDIF
SHELL '%comspec% /c @LDRIVE\tools\ntname\ntname.exe @userid > c:\ntname.txt'
$null = OPEN (4,c:\ntname.txt)
$result=READLINE(4)
$null = CLOSE(4)
DEL "c:\ntname.txt"
IF $result
	$error="Multiple logons not allowed, according to our information you are already logged on to $result"
	$tijd=""
	$actie="U wordt nu automatisch uitgelogd"
	CALL (@LDRIVE + "\errorscript.kix")
ENDIF
:NANTNAME