I'm a doctor and about to complete my residency training this year thus my H1B expires on June 30, 2012. I have a multiple entry B1/B2 visa stamp valid till 2017 on my passport. I need to take the boards here on aug. My question is can I leave the US and go home then reenter the US like say end of July to take my boards using my tourist visa? How will I know if they ever cancelled it?