Filter templategrid by reference set

I've got two objects which are connected by a reference set: Case Attachment One case can contain many Attachments. Now I'd like to display attachments in a template grid (in the dataview of a Case). The template grid in the dataview Case should only display attachments which are connected to the Case (like you can do with a reference set selector). Is there a way to filter the attachments by Case? I tried to do this using an XPath constraint, but could not get it done.
1 answers

Sure you could just put an XPath on the grid looking like [MyFirstModule.Attachment_YourCase = '[%CurrentObject%]'] (depending on the name of your association) but why not use a path to YourCase when you add a template grid of Attachment? Or is the association parent on the wrong entity for that?

I'd probably model it with the owner being Attachment and it just being a reference if your case has multiple attachments but attachments only have a single case.