[Zope] Calculating how long time a user spends on a page

Hello, I need to find out how long time a user spend on a page in my zope site. Guess you can do that by a session/cookie, but I don't know anything about it. Anyone who has tried to do something like this ? It's for a cinema that plays movies (pay-per-view), so I need to count the minutes from the movie begins to the user exits. Any good ideas ? Regards, -- ************************ Gitte Wange Jensen System Squid Developer MMManager Aps +45 29 72 79 72 gitte@mmmanager.org ************************