[Zope] Newbie - ZCatalog expression from REQUEST object?

[Lonnie Maynard]

I have what is quite probably a stupid newbie question and apologize in 
advance. I have configured a ZCatalog with custom indexes and wish to do a 
relatively simple search on that catalog via the code below. 

<dtml-in expr="Catalog(start_date=ZopeTime(),
              start_date_usage='range:max',
              end_date=ZopeTime(),
              end_date_usage='range:min',
              com_search='<dtml-var name=searchterm>'
              )"> 

start_date is used to limit returned items to those that have a start_date 
earlier than today, end_date is used to limit returned items to those that 
have an end_date later than today. Both of those work. My issue is passing 
the Request object searchterm. It is in the namespace, as I can show the var 
above the dtml-in line. 

I have tried 1.   <dtml-var searchterm>
            2.  <dtml-var name="searchterm"> (I get invalid attribute name)
            3.  <dtml-var name=searchterm> 

1 and 3 return no results, and #2 gives me invalid attribute name. It looks 
as if I have bad syntax but I do not know where. Any help would be greatly 
appreciated. Thanks in Advance.  Lonnie Maynard