How to get the Post position in a thread (post #) for a given postid?

[jwocky]

So I have a post-id and the thread-id for a post, but I cant figure out how to find out where in the thread this post is (the post #).

The reason I need to pull this data, is to figure out what page the post is on in a multiple page thread. I figure if I can find the post # then I can divide that number by the # of posts per page, to figure out what page the post is actually on.

Thanks!!