[Zope] update existing instances of a class?

Aloha, I have a python product that I have modified (most importantly by adding some properties). Some instances already exist that were created prior to adding these properties. I have heard it is possible to update the existing instances (so that they get the new properties) - is this true? If so, where might I find info on how to do this? thanks, John S. __________________________________ Do you Yahoo!? New and Improved Yahoo! Mail - 100MB free storage! http://promotions.yahoo.com/new_mail