[Zope] variables in path expressions

[Mark Gibson]

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