Block New Threads after x amt of post

[Yahhoon23]

Hi, my request is as follows.

I have a section on my forum for Buy/Sell/Trade and I have an area where Dealers can subscribe for a fee and are able to sell as many items they want.

Since regular members can make as many threads in the regular B/S/T Area, it really takes away from the dealers who are properly paying to sell things on my site.

I'd like to set it up so members can only create say 5 new threads per month in that area. Meaning they can only sell 5 items in a month. I want them to still be able to post in that area if for example they see someone selling something, and they want to buy it.

My only downside is, the fact that if they are Wanting to Buy (WTB) an item they won't be able to create a thread at all.

So basically, I was wondering if there was a way to make it so I could allow them only to make x new threads per month and they could post as much as they wanted, and maybe somewhat of a check on their threads.

For example, if they reached their 5 thread limit, all they could post was Threads that Started with WTB: (Want to Buy) and any other thread would be disallowed.

I know, my explanation is pretty confusing, I think I just confused myself. But if anyone has any insight, I'd appreciate it. Maybe even feedback or recommendations on what I am trying to do. I'm not sure how intensive this would be on the site and server if it had to run a check on the title of every thread that is posted, or if it's even possible, but I figured I'd give it a shot.

Thanks

[Yahhoon23]

Anyone?