Wolfgang Strobl writes:
 > "Finding"a bunch of DTML Documents into a Zcatalog is easy. 
 > But how to do that programmatically? I haven't even found a way 
 > of doing that for a single DMTL Document. 
You call the catalog with your search terms as keyword paramters:
    <dtml-in "catalog(principia_search_source='cool and new')">
      ....
    </dtml-in>
Have a look at the two ZCatalog tutorials on zope.org.
Dieter