Removing vocal from an existing professional and commercial song is one of the most frequaltly question that comes from non-professionals or amateurs who believe that the computer can do miracles
There is no way to do that... BUT I can suggest to stay tuned with Melodyne developers and his new research about "Direct Note Access" (DNA) technology.
check out over-there:
http://www.celemony.com/cms/index.php?id=dna
The extended features of this extraordinary technology could give, in the near future, an affirmative answer to the question of this thread!
However, will always be absolutely necessary that the software will be used by qualified personnel in order to obtain a professional result! (and the singers and musicians must be "BRAVO" OR "BRAVI"!!!)
G