cross referencing excel spread sheets eliminating redundant data

[farmboy]

well heres my problem maybe simple for some but i'm having a heck of a time coming up with a equation that works. I have 4 excel spred sheets titled 2007,2008,2009 and 2010 each of these spread sheets contain numbers identifing the box that had repairs done on it in that year. So I need to find a way to cross reference between these spread sheets to come up with a list of box numbers for a 2010 warrenty list the company will only warrenty each individual box number once so if we have fixed the box in 2007,2008 and 2009 then it cannot be warrentied in 2010. Box numbers are located in column B3 and down in each of the spread sheets. I should have my excel document attached let me know if there is anything I can do to clairifiy my problem.

Thanks for your help

Clay