In many companies, business logic resides in Excel. This business logic is sometimes created by business analysts and sometimes by business users who want to automate parts of their everyday job using Excel. This same Excel-based business logic is often copied into an application (i.e. a website) and is maintained on 2 places: if the Excel logic changes, the application should also be modified.
On his blog, Maarten Balliauw tells you how you can use PHPExcel to take advantage of the Excel-based business logic without having to worry about duplicate business logic.