[Zope] WebDAV, Web Folders and collaborative work

I am trying to unravel the mysteries of collaborative document editing via the web.There looks to be a lot of potential in the WebDAV stuff, but I think I am missing a brick from the load: I am happily dragging and dropping documents between my Zope server and my desktop using the 'Open as Web Folder' facility of IE5. This seems to save me from writing an upload page but not much else. What I am looking for is a way to prevent others from editing the document whilst I have it. I thought WebDAV helped with this. Maybe I need to do something with a Version? have I missed the point? Regards Neil