Select all cells to be formatted and then

Try conditional formula:

=And(A1="Need",$X1<Today()-15)

Where A1 is the top-left most cell of your selection and X1 contains the date in that same row. (Note: the $ in front of the X to make sure all cells refer to that column always).

To invoke CF in XL2007... choose Conditional Formatting from the Home menu and then select New Rule.. then select Use formula to determine which cells to format.