Just noticted there was a page 2 of this thread - doh!.
I can see the sense to doing it this way, but I think I would find two libraries harder to manage. Now I have a shortcut key to clear the spreadsheet makes it really easy. I also have a "BooksAdded1DayAgo" VL that I edit to make it longer if needed. That's what is so cool about calibre - lots of different ways of doing things.