Checking for elements

Hello All,
 I'm new to all this and I'm looking for some direction.
 I need to be able to check an XML document for some specific elements, and if
possible produce a little report on which ones are missing. The document has
already been validated against a dtd/schema that contains approximately 270
elements, but I need to check that the ~40 I need are present. If they aren't
present I want to produce a little report that says which elements are not present. 
 Can I do this with XSLT, or is there an easier way to do this?   

Thanks,

-- 
Noah Genner