[Zope] kind of variable in a document

Hello, I am trying to display a sequence of numbers with next to each of them the cumulated value of the previous ones. Thus, I was trying to declare a variable buffer to add at each cycle the value of the new number. But I can't figure out how to create a variable. Can somebody tell me how to declare such variable? Thanks, Laurent -- Laurent Chane-Chuen-Kee A X I O M (Cambridge) Ltd. Tel: +44 (0)1223 810 305 Fax: +44 (0)1223 812 889