how long it takes to process h4 to h1 conversion through COS?


I have an h4 visa. My h1 got approved 1 month back. Can I change my visa status to h1 with out travel to inda? I recenly got an offer from one of the company and they want me to join in 2 weeks time.I read about COS(Change Of Status) and if I apply for COS how long it takes to procees? Can anyone help me on this?