Advanced forum access / post count relationship?

[DR EVYL]

I couldn't find anything on this one, so I thought I would post it to see what you thought... It probably sounds a little like a "lockdown" but it isn't...

I'm using vBulletin 2.2.1 with PHP 4.0.6

What I would like to do is set up one forum on my VBB so that users with less than X number of posts in a 30 day period have that forum removed from their access. I'd also like to set that forum so that users must have X number of posts in order to see it in the first place...and I've already read the threads on that hack.

Example: My board is an ages 18-up board, and there's a porn forum that gets a lot of traffic.... one of the problems I have with this is that currently 75% of my user base simply logs on and lurks in the porn forum, and I want to drastically reduce the number of freeloaders on my board.

What I would like to do is set up the porn forum so that (a) a user has to have X posts to see it, and then if they don't continue to post, their access to the porn forum is automatically removed. If they post again in a different forum, I'd like to have it regrant their access. I still want them to be able to see all the other forums they normally would see, I simply want the porn forum removed from their access.

Currently I'm doing this manually, but I can see as my user base increases, it's going to be a bear to manage.

Is this something that is possible? Is there already a hack like this I may have missed?

Thanks in advance.