I am new to Crystal reports, I have a basic SQL table with information but not sure how to do this formula.
In my table I have a Year ,Product and Value column.
In Crystal I have a cross tab with Product on the left and Year at the top,
giving the value per product for two years.(eg. 2008 vs 2009)
I want to write a formula calculating the difference between the two years
per product.

Any help will be appreciated