I tried smth like that but didn't work. Probably i couldnt construct the conditional with a specific categoryid.
Code:
if ( $vbulletin->forumcache[$categoryid] == 48 AND in_array($foruminfo['forumid'], split(',',$vbulletin->forumcache[$categoryid]['childlist'])))
Also i wonder if that conditional works if it's not a category but a regular forum with many subforums under it.