Hi
say column B

Highlight B2:B22
Look top say Conditional Formatting click on,
click: Manage Rules,
Click: New Rule,
Click: Format only cells that contain,
Keep "Cell Value", next "between" change to "Less than", next =TODAY()+15
Click: Format,
Look top click: Fill,
Click: any colour you choose, (Make sure you see colour in Sample box)
Click: OK ,
Click: OK,
Click: Apply,
Then it you done!!.

Regard
micope21