That is a very cool idea for a feature. I haven't used databases much
in general, so I don't know much about existing features, but I could
see how something like that could be very useful to a master trying to
refine their opening preparation. At my patzer level (1400ish USCF),
it's something that could be cool just for the sake of curiousity.

So is this a free program? As I said, I don't know much about chess
databases (which is ironic, since I specialize in SQL databases in my
profession). I'd like to get a database program and a large database
of master and GM games eventually, so I can see how better players
than me handle certain openings and the positions that result from
them. For now, I tend to just go to chesslab.com and look at games
there in the openings I play.

--Fromper