Firstly, don't panic... do the items end at the same time on the same day?  If they don't and end on different days, then you have some options.  See how the first auction goes... if you win it than cancel your bid on the other listing or contact the seller to cancel your bid due to 'the dilemma'; if you don't win your item on first auction, you are still in the running to win the other.  If they do end at the same time on the same day, then you need to cancel your bid on one and stick to your guns on the other.  Look up ebay help pages regarding cancelling bids if you are unsure how to do this or contact the seller - they can be pretty understanding of your situation, when given enough notice, usually having been buyers themselves.  Failing that, if the seller is less than compliant, contact ebay customer service direct and explain your issue and what you would like to do.  Make sure all the correspondence you have with the seller, if any, is done through ebay messages so you have proof to back up your request.

Hope this helps and happy ebaying!  🙂  healthwise2011