Classified adverts hack

[Spinball]

Hi folks, I've seen the other request for a classifieds hack and a suggestion to use photopost classifieds.
I would prefer to use something completely integrated with vb so that the threads are searchable etc.
The problem with classifieds forums is that in a successful forum, posts shoot off the first page quickly.
Splitting them up seems an obvious solution.
I have already implemented Erwin's form to thread hack for our classifieds (screen capture attached) which works well to encourage people to read our trading rules.
I think, however, that adverts need to be splittable into ad type (For Sale, For Trade and Wanted) and ad category (Amplifiers, Speakers, TVs etc in the case of our forums).
I could probably add a couple of fields to the post table (a drop-downlist for each) for the ad type and category and have the form to thread hack populate these in the thread (or post?) table.
But having a specific search for the classifieds forum which produces the correct results is beyond me.
Can anyone help? I suggest that if programmed properly with a nice admin interface, this could be a significant and popular hack.