Download monitor

This is probably a topic for gurus. I'd like to have some way of knowing, with PHP, when a download is finished. My site offers several files for download, and I want to make sure a given user does not download more than one file at a time. I know there is a way to do this with an Apache module, but I'm using Apache for Windows and I really don't feel like writing my own module for connection management. Users are people with sessions, so I have access to session vars and since I use a database I also have acces to MySQL tables. The configuration I use is as follow: - Apache 1.3.22 - PHP 4.1.1 - MySQL 3.23 something Again, my goal is to be able to tell when a given user has finished a download so I can give him permission to start another one. This could be done in anything, PHP, javascript, Java, I don't really care. Any help appreciated. Olivier Hubert