* It is possible, once the start/end conditions select well balanced
  content, to find them. I don't have all the logic worked out (we're
trying
  Sourcerer as an easier solution), but the pseudo logic I had
tentatively
  mapped out looks something like this:

        <xsl:template match="processing-instruction('FM')">
                * if contains 'CondStart'
                        * capture the condition name
                        * select all sibling nodes and process first-one
in a re
                          Recursive call:

Cheers,
Wendell