[Zope] searching back through the enclosing documents.

If I have a number of DTML documents including each other with <!--#var document1-->, then inside document1 referring to document2, and so on, how can I, from the innermost document, walk back up the calling chain of documents, looking at each on the way? Using acquisition just gives me the chain of folders from the innermost document back up to the top - not what I want. Thanks, Anthony