[Zope] How do you do this?

Suppose I have a domain say "mydomain.com". I want to set up n subdomains for user1, user2, ..., usern of the form "useri.mydomain.com". Typing "useri.mydomain.com" in your browser would take you to useri's home page. How do I set up Zope so that useri's pages are served from Zope (actually Plone)? Best Regards Ian Nunn