[Zope] multi-column sort with ZCatalog

Hello all, I have a simple ZCatalog query with a sort_on and sort_order being passed to it. Is there any way I can do the sort on multiple columns? This seems like an important feature. I've heard that is not possible, but I'm wondering if I am just missing something/getting wrong info. I'm already looking into the Generic Sort External Method, but I'm wondering if there is some other way to do this? Thanks, ~Mark