[Zope] Search Interface

I'm having some trouble setting up a search interface into a ZCatalog. I want to create a text index on the contents of my DTML documents, but I can't seem to get it to work. It search on title just fine. I think my problem is that I don't know how to create the right index, and what to call it (how the body or text of a DTML document is referenced). Can anyone enlighten me about this? I might be going blind, but I haven't come across anything in the documentation so far that answers my question. I'm about to resort to reading the Zope source! (which I think I will need to do sooner or later anyway, to get a better understanding of how it all works). Thanks for any assistance. David Trudgett