[Zope] How to touch session_data without fingerprints???

Hallo, I want to transparently touch the session_data. When I call functions like REQUEST.SESSION.hasSessionData() or getSessionData(create=0) I create the new object in transient object container. Is there any way to avoid it and check if session object exists? Or if not - how to delete only my session object from container? I can use external functions if necessary. All the fuss is about counting logged users. I want to limit that number, and I do it by counting the number of session objects - already done. The problem is that I can't check the number without increasing it :( Maybe there is other way. Pawel Lewicki