[Zope] DTML Newbie: Using variable as an object in path?

I'd like to set a variable in a DTML document, then call another DTML doc and use that variable as part of an object path:, eg: <dtml-with a_folder_name.the_variable_value> so I can use different objects (files) by passing the filename in the variable. How can I do this? Also, is the correct way to set a DTML variable to use dtml-call REQUEST.set or is there another way? Thanks in advance, Patrick Price