The easy way to track cell changes in Excel and then do something when those cells are changed.
This method shows you a simple system that has 2 parts: one in the worksheet and one in VBA - but don't worry because I show you how to do everything and change it for your situation.
There is NO complex VBA in this tutorial, I promise! :)
Events in Excel (Msft link)
Change Event in Excel (Msft link)