Allow ability to combine metrics using arithmetic in the screener

Allowing the ability to combine metrics using arithmetic on the screener would open up doors and allow for much more flexibility. One example I am thinking of is to screen for Net-Net stocks. Currently, we can screen for NCAV & Market Cap but have no way to screen out stocks to show only those that have Market cap <67% of NCAV, as Ben Graham suggested. I do this now by exporting an entire report of the stocks database and doing it myself in excel but it would be nice to be able to do it within the app if it wouldn't be a hard thing to add/update.