[Zope] Virtuel hosting

Hi If I have a product made in python installed on my zope-server, let's say an addressbook application, and I want to be able to change some things in the application for some of the sites on the same zope-server. It could be that some users didn't like some of the properties displayed or something like that. Some of the forms ect. are defined in the /dtml folder under the product. How can I handle that? Regards Jens