[Zope] dtml-in and totals

Hi *, I have this piece of DTML... <dtml-var expr="(wi_extrtlty - wi_extrtlly) / wi_extrtlly * 100" fmt="%.2f"> which works fine. At the end of my report I want to display the total in my <dtml-if sequence-end> and can't understand why this won't work... <dtml-var expr="(total-wi_extrtlty - total-wi_extrtlly) / total-wi_extrtlly * 100" fmt="%.2f"> Can anyone shread some light on this? Regards, Michael