[Zope] webdav upload - controlling type, hook

When uploading a file to the zope db using the webdav interface zope select on object type based on the file contents (or extension?). For instance when I upload a html file it becomes a DTML document. Is there any way to control what type of object is selected? Additionally I would like to execute some script code after a webdav upload. Is there any way to get a hook or callback or something similar? Thanks, Jakob