I need to calculate with a formula the date of someones next birthday based upon a pre-determined date. For example, I need to calculate the date of a person's birthday based upon a start date at work:

Start Date - 12/2/1999
Birth Date - 08/01/1956
Formula Result - 08/01/2000 because that would be the next birthday for this individual based upon the start date of 12/2/1999.

I simply cannot figure out how to do this with a formula - can anyone help? I'm using Excel 2010 in Window's 7.

Thanks,
Robert G