This feature suggestion is constantly running in background in my head :)
I think the best way to implement it is to provide a new menu item in the drop-down Tools menu of the filter box. Name it, say, 'Check values from Clipboard' or `Select Values from Clipboard`. When it is chosen, we clear all check marks in the item list (not the custom filter section), and check only those which are present in the values stored in the clipboard. We may also display non-existing members in italic - AFM can already do this. How is about that?
And can you also tell us, how often this functionality is used by the end users of your app and whether adding it to AFM can save much time for them? If possible, show some examples of data for which this feature would be extremely useful.