Dale
I have tried this using the PG vocal remover plug-in. It did not do a good enough job for what I was doing.
Any vocal remover works on three principles:
1: something centered in the mix.
2: level
3: frequency

Because of this you will lose something when you try to remove vocals.

With the PG remover I found it would pump (Compress heavily when vocals came on) something terrible. It also did not really remove the vocals. During the vocal parts the music would almost fade to half volume.
It just didn't sound right or good at all.
To me it was unusable results.

You can access this by putting the mp3 on a track in PTPA. Call up the DX effect for the track and call up the vocal remover.
Good luck, I hope you have better results.

Be blessed
Bob