Member Permissions Posibilty?

[MPDesignZ]

I need to know if there is a hack that will limited a member to a usergroup no matter if they get promoted to another usergroup. I have 3 promotions on a forum and what I need is a hack that will promote members when they reach 5 posts to a specific member group, but when they get the next promotion at 10 posts they will still keep the promotion from the 5 post group in their profile so they can view a specific part of my web page as well as have the 10 post promotion. Is this possible?

Or is it possible to limit the public groups to where a member has to have at least one post to join any public group on the forum?

MP