[Zope] variables in path expressions

For your consideration: <span tal:omit-tag="" tal:repeat="thepage python:['pageA','pageB']"> <span tal:condition="nocall:here/thepage | nothing" tal:content="structure here/thepage"></span> </span> Basicaly, I want to test if 'pageA' exists, and if so, render it. I'd like to do something like tal:condition="nocall:here/$thepage | nothing", but this doesn't seem to work. Any ideas of how to do this? Thanks, Mark