Retrieving Body Of A HTTP Message Being Posted To A Listening Asp Page

I have an ASP page that sits and listens for responses sent to it by a third party. The third party simply sends a plain text delimited response in the body of the http message.

Eg: Account=2,User=92663,Pass=OK,Action=5

What I can't figure out on my listening page, is how to capture the body of the message being posted to it, so that i can then manipulate the delimited string, and split it up into the variables for later use.

How do i get access to the body of the http page? I thought perhaps using WinHTTP, but it looks like it only works when your page goes looking for a web page, and not when a page is being submitted to it, like in this case.