[Zope] Referring to a total-xxx variable

Following on from my last posting I seem to have made a lot of progress - although still not sure if what I have done is the right thing or not. However, please somebody put me out of my misery. In the following code snippet the dtml-var part works fine. How can I, therefore, add count-id to v_allItems? It seems to think I am trying to do subtraction. I've spent a couple of hours trying to find the mystical incantation. <dtml-in "PARENTS[0].objectValues(['TimeSheet'])"> <dtml-var count-id> <dtml-call "REQUEST.set('v_allItems', v_allItems + count-id)"> </dtml-in> Ian Cottee Nagoya, Japan