Well, I think if you get a pen and paper and try a couple of dates, you'll see the basic math problem with storing the dates as mm/dd/yyy. You have two choices. One is to represent the dates as YYYYMMDD, so that two dates can be compared. The other is to store the dates as date datatypes, and use the dateDiff() function to do the compares. If you look up or Google the CF dateDiff function you'll see how to use it and how to create date datatypes.
-reed