[Zope] Dynamic sorting in <dtml-in>

I feel like this should be easy, but I'm scratching my head try to remember if I've seen an easy solution. I'm doing a standard objectValues dtml-in: <dtml-in objectValues> <dtml-var xxxxx> </dtml-in> But I want to sort it by the attribute that is passed in the URL. I looked at the DTML source of the Zope site (where they do this), but didn't see how their sort_on was being used. Of course, I could do this as a python script, etc.--but is there a Q&D DTML way? Thanks! -- Joel Burton <jburton@scw.org> Director of Information Systems, Support Center of Washington