using adobe audition to create the mono wavs for each channel
sonic foundry soundforge to scan the track for the normalisation values for the Sonic scenarist Ac3 encoder to then encode it.
I know that's a short answer but it's getting late here and I think this question really deserves a fuller answer which we can put into the relevant forum for everyone to learn from.
its not hard, but it does take a bit of trail and error + time to do.