[Zope] User passwords

I asked this one before but got no response. That's surprising because it seems like it should be a simple thing. I've set up a bunch of users in the acl_users folder. I assigned their passwords manually. I'd like to give them a web page where they can change their passwords themselves. Surely there must be a simple way to do it without going to a separate authentication module like CookieCrumbler or some such. Does anyone know of a simple way to change user passwords? Joe Goldthwaite