New H1b Stamping with Old H1b Stamp and New I-797

In May 2011, I got my H1B transferred from Company A to COmpany B where I am working currently.I just got a new offer from Company C and they have filed for my H1B transfer and I'm expecting approval within 1 week from today.Now on my passport I have H1B visa stamping of Company A till
April 2013.I got this stamping done at U.S consulate in Mumbai when I made a trip to India in November 2010. Now I am planning to make a trip to India in January 2012 and I will be with Company C at that time.My question is, Do I need to go to U.S Consulate again for visa stamping as I have changed my employer from A to B to C? OR I don't need to go to U.S Consulate as H1 visa (with stamping from Company A) is still valid till April 2013? In that case I would only need to show the visa office my new I-797 from Company C when I return back to U.S.A after my vacation is complete,correct? Any help in solving this dilemma will be greatly appreciated!Thank you very much ahead of time for your responses!!

You should not have a problem entering with your existing visa and the new notice of approval.

Please let me know,if anybody ever had any problems at port of entry for holding old h1b stamp and new i-797.Your response on this will be highly appreciated.