If he's submitting forms, which he said he is, then it's either posting to itself or to another page. In either case (not to mention the case of simply clicking on links) he'd have to change the link on the page his browser is viewing to reference your CGI script. If he's able to do that, either he's got access to the server itself (and, even then, it would be far more difficult than just changing some links) or he can change the page on the fly in he browser, in which case he has enough capability to have the browser itself count, and the other script and web server wouldn't be needed.

The only way your idea will work is if the only way he ever gets to any page he's interested in is by typing it into his URL bar (or selecting a bookmark), but never by clicking on a link or submitting a form.