[Zope] How to insert a DTML doc given its ID as a string?

Must be trivial. Can't find answer. 'thisWeeklyMain' is a Python routine that supplies the name of a DTML doc that _might_ exist in the current folder. I'd like to arrange to insert the DTML doc, if it exists, or an alternative doc, if it does not. Thanks for your help. Bill ------------ "It is the time that you have wasted for your rose that makes your rose so important."--St-Exupery