Private Fora and Usergroups

Okay I'm having a really hard time with this specific problem, and I'm hoping I don't have to right my own code for it, because I'm horrible at it.

I'm Admin of a gaming forum and they have guilds ingame, and I want them to be able to have their own private guild forums on the site. The problem is, I can do it passworded, but what about when someone is kicked out of the guild, then what? They still have access, that sucks, you'd have to change the pass and everyone remember it again.

So the only solution I could think of was to have a way wherein the guild leader could create a usergroup, or I could create a usergroup and name the guild leader, the leader of the group, and from there the guild leader be able to add who s/he want and I be able to simply give them and ONLY them privilege to that sub-fora.

My problem arises in having the group leader be able to add others. I can't find a way for that to happen, I've been looking up solutions online and can't find any, so I turn here, hoping someone may have the answer.

I dont think that is possible, unless you give the guild leaders admincp access.

If you do it the password protected way, you can use a mod at vbulletin.org that bans a user from a specific forum and not the whole site. Maybe that can help you out.