[Zope] Access Rule

I asked a similar question on the plone mailing list, so sorry guys for a repeat. I created an access rule in Plone, not the root and I need to find if a user is logged in. I was told that can't be done, but doesn't there have to be a something transferred between pages to tell if someone is logged in. A session variable set somewhere or something. I figured maybe this was more of a Zope thing than Plone. Thanks! Andrew R. Halko