I realize you are asking about Bridge/Photoshop, and I don't know the answer.
But it is possible in Lightroom using a plugin, e.g. Paddy - dunno whether that does you any good or not..
I've never heard of it being done, but that doesn't mean that it's not possible. Are there such a thing MIDI drivers which convert control signals to key presses? That would be the first thing I'd try.