To my knowledge about that kinda software i sorta doubt there is.
my best bet would have to be using fansubs that need special extensions to view their subtitle work.thus not letting the subtitles come through.
or just find that raws that are out.(they're easy to get.) <i'd go with this
Making AMV's rule number 11, 'dont use subtitles unless you are willing to insert a small black bar to cover them" (it also creates a cinematic effect if you do :P)