[kh99]

Where are you getting the userids you're processing? If you're doing a query for them, you might be able to add in the usergroupids and membergroupids fields from the user table. If you aren't doing the query for the userid, then you'll have to do one yourself. Then you might be able to use is_member_of() (which maybe is the function you were talking about), and pass it a $userinfo array (which has to contain userid, usergroupid, and membergroupid).