H1 B Transfer to a company while H1B transfer is pending


I have an approved H1B petition from company A which is valid till 2015. I got a new offer from company B and filed for a H1B transfer and currently working for company B but the H1B transfer is still pending. Now I received another offer from Company C, which I really want to join.

Do I have to wait for approval from company B to transfer to company C?

Can I transfer to company C using company A H1B approved petition?

Please help.!!

Thanks in advance.

Can someone who has gone through this or has knowledge about this situation please answer… I am really worried…!