What is the success rate on having a vasectomy reversed?

My fiancee and I are wanting to have baby together. We both were in previous marriages. I had 2 boys and he has 1 boy. He had a vasectomy (he got fixed) done after his divorce and now we were wanting to have it reversed. We want a little girl so bad. I was just wondering the ratings and if it would more than likely work or if we are wasting time thinking about having it reversed. Thanks!