How vBulletin handles sessions - integrating into main site

[poi@nwdnb]

I've currently got my forums running, and i've also built the main site on the same domain, that runs using ASP. The ASP pages check the forum cookies etc to verify that a user is logged in, and i have extended the vBulletin database to incorporate all the extra information to be displayed on the main site.

So i can do things like, on the main ASP site, run a query which checks how many people are browsing the forums (by looking at the session table) etc.

What I would like to do though, is to have the ASP page update the session table each time a user moves about the site, so that users who are just browsing the site, and have not visited the forum, appear online aswell.

Can anyone give me some pointers on the steps i should take to update the session table? I've looked through the PHP code and its quite complex, i'm not fussed about it recording WHERE the user is browsing (the session table stores URLs etc) - i just want it to show the user as online..

Any help greatly appreciated.