VB permissions = fail. How do I make a hidden forum for select users only?

[rnadmo]

I'm having huge problems trying to make a hidden forum, that only a set number of users can see. I don't want to put these users into a new primary usergroup as I have the subscription system running so I have Members, and Supporters, and the supporters can see a few extra forums that the members can't access.. that's all working fine..

I just need to be able to tag a few friends so they can see a new hidden forum, but it be completely invisible to everyone else, so they don't even know it exists.

I've been trying for days.. and each time I -think- i've got it working (using a few test accounts i've made).. suddenly a random member will post in the "hidden" forum.. when they're not even supposed to be seeing it.

Please help! Paypal reward will be considered.

Cheers.