[Zope] sorting a catalog - order

This is probably really easy but I can't find it anywhere in the docs. I can iterate over a catalog just fine, sorted, for example: <dtml-in Catalog sort_by=bobobase_modification_time> ... </dtml-in> But how do I sort in reverse order? thanks much -Kevin __________________________________________________ Terrorist Attacks on U.S. - How can you help? Donate cash, emergency relief information http://dailynews.yahoo.com/fc/US/Emergency_Information/