[Zope] sequence-item: how do I use it in an expr?

I know I ask a lot of silly questions, at least I'm learning...In the following snippet 'build' is a list of integers. Now I want to do 'prBuildInsertMethod' with all the values in 'build'. To the untrained eye, it seems like this should work. But Zope can't find variable 'sequence'...why? How do I do it then? <dtml-in builds> <dtml-call expr="prBuildInsertMethod(buildNo=sequence-item)"> </dtml-in>