You can try to by doing this: Use a long towel and start bay grabbing the very ends of it, start with the towel in front of you sand raise your hands above your head and try to take the towel all the way around until its behind you. I would do this standing in front of a mirror. Its really important that you kkep your shoulders down and back, dont shrug and try to keep your hand even with one another throughout the entire motion.
http://www.youtube.com/watch?v=Y6Nrx...eature=related
The guy in this clip is doing it a little fast, take your time with it, it wont be easy at first.
I had re-constructive shoulder surgery 11 yrs ago and from time to time it flares up on me. I use this stretch everytime my shoulder starts to bother me and it works.
Good luck bro.