Having done some google searches with no result and referenced again the Zope book on DTML, I assume what I am trying is either very trivial or dumb: I want to do some math in DTML, here an example: <dtml-let myCounter=0> <dtml-in expr="some_method(_['a_current_id'])"> <dtml-if checked> <dtml-call expr="myCounter=myCounter+1"> </dtml-if> </dtml-in> <dtml-if expr="myCounter>0"> DO SOMETHING! </dtml-if> </dtml-let> "some_method" returns a sequence where some items might have an attribute "checked". So while I iterate over the sequence I want to change the value of "myCounter". The code above generates Syntax Errors. I tried referencing myCounter with the underscore, no luck. Any help appreciated. If there's a web page that explains a little how to "manipulate variables using DTML", I'd be really thankful to know. Cheers Marc