[Zope] Password

I'm trying to build an interface to allow users to change their passwords (only their passwords). I have no problem getting the new password and changing the old one. The problem is a professional site would ask the user to enter their current password and verify it is correct before they allow the user to change their password. The question then is does anyone have any ideas on how to compare a user entered password to what Zope has stored as the password? Thanks, DR