[Zope] How to I get column totals?

Hi, I have a SQL query that returns columns of numbers. I'd like to add these numbers together and display the total at the bottom of the page under each column. My question is, as I move through the returned rows how do I add the current value of a field to the sum of all previous values of a field? I'm sure this is very easy - but my mind is fried from the work week and I'm just not thinking about this clearly. I've searched the lists and I can't put the right combination of search phrases together. I suspect this will be a python script solution rather than DTML. Pointers to docs or how-tos I've overlooked would be helpful. Thanks! Mark