Looks like you're going to have to put a huge 
disclaimer on your auctions outside of the 
general shipping information space Ebay sets 
aside. Set a standard price for shipping on cels 
and make it in big lettering that you will not 
honor auctions to international buyers or that 
you will cancel their bid. You have a right to 
choose how you want to do business, you don't 
have to deal with the haggling or the confused 
foreigner if you don't want to. It may limit your 
customer base but that is still your choice.