[Zope] Z2.log and authenticated users

Hi, is it possible to force zope to write the authenticated users in the Z2.log? The only two users that I see in this file are "Anonymous" and "admin". The later only appears if it logs through the manage interface. The reason of doing this is that I would like to process my log file with a log analyzer like webalizer in order to see which user has more accesses. Thanks in advanced, Josef.