I wish I knew how to do that I know you can do it with MLB.TV but who has the money for that ? (And evil blackouts).
If the radio broadcast was behind he TV broadcast I could do it.
I do it the latter. Since I can't get an actual broadcast signal living in Nebraska, I've got to use the internets for the audio which is about 30 seconds behind the EI broadcast. Takes a bit to get it to match up but it works pretty well.