If you had all of the cards listed that you have of your PC. You could go to the page of the players and click on collection summary then click on add/update. At that point there is a pull down You can pick what you want to look at. The Do not have shows all the cards you have on your want list and what is new (or cards you have not list on your want list and in your collection)
There is a new feature that I have asked for which would have ONLY the cards that you have not listed on your want list or in your collection. New Feature Tracker | Trading Card Database (tcdb.com)
Hope that helps a little