How can I extract vocals from a track to use as an acapella?

Hi, just as the title suggests I would like to know how to extract vocals from a song so I can then use it as an acapella using Audition CS5?

Also whilst I'm here, again using audition CS5, how can I determine the bpm of whatever sound file I have open, and furthermore how can I then match the bpm from another sound file to match the bpm of the track I'm working on?

Thanks for your time

Dan