I just used the GroupMembers UDF and threw this together in a couple of secs... I tested it with an IP (like in your example) but it didn't work. However, using the actual computername did work.

Code:
 
break on

$target = "computername"
$group = "Administrators"
$UserID = "administrator"

$Members=groupmembers($target,$group)
For Each $member in $members
  If $userid=$member
    ? "hello"
    ; Do something
  else
    ; Do nothing
  endif
next
_________________________
(... better days ahead)