custom mod/hack user rights in vbulletin

[bituman]

With the link provided i could add user group permissions.. half of a success..
I am far from being familiar with vbulletin, how can i add permissions for a specific forum?

I will grant the user admin permissions in the cms if he has the cms_admin permission not generally, but on a specific forum, so i can use:

$forumperms = fetch_permissions(3);
if (!($forumperms & $vbulletin->bf_ugp_forumpermissions['is_admin'])) {