Best Adsense configuration within posts
 

I have found that the 336 x 280 rectangle at the bottom of the first post (within the post, not below) converts great... in fact, it's by far my best. But adding that in is easy since you can do so within the Ad Location Templates. So my question is, how can one configure it so this same Adsense configuration is replicated within X number of posts.... i.e. within the 1st and 10th post, or every 3 posts, etc.

Ideally, what I would like to do right now is try it out within the first post and the last post, but only if there are, say, 3 or more posts within the thread. Because otherwise it would be ad after ad if there were only 2 posts.

Any Adsense/vB gurus out there know how to do this? I'm running 3.7.5 on this particular forum I'm working on.

thank you!

--------------- Added [DATE]1248843179[/DATE] at [TIME]1248843179[/TIME] ---------------

No one can help with this? Believe it or not I've searched on these forums and on Google for hours and haven't been able to find this.