Adsense question…

I’m trying to figure out a way to automatically include an adsense ad in ONLY the most recent blog posting (I’m referring to the main page with multiple blog postings, NOT single.php)…

The catch is that when I publish a new story, I want the adsense code to be removed from the story that is “second-newest.” From what I understand, the same adsense code can’t be used more than three times on the same page, and I have ten blog posts per page so obviously it won’t work.

I realize I could just put in the adsense code manually for each post, and remove it from the second post, but I’d like to find a way to have it automated (if possible).

Thanks,