In example: I want to compile a list of DTS LDs I don't own. It would be nice to have an option in advance search where I can filter the titles I own so my search would return only the DTS LDs outside my collection.

I just added the positive where I have to list only titles hitting the collection (ALL MATCHING -AND- IN_COLLECTION):

Your request is a little more complex: ALL MATCHING -MINUS- IN_COLLECTION, that probably requires a nested request (where x in (select ...))

Will require a bit more of time to test.

Julien