Pivot table calculation. Showing differences

Hello,

I'm very familiar with pivot tables, but can't solve that problem. Attached is a copy (sample) that describes what I'm facing. Basically I have products and 2 periods (In program and not in program). I need to see the difference in price between the same product while in program and while not in program. This is simple if the number of products does not change like shown in my workbook. The number of products might increase or decrese depending on the selection. How can I keep showing that difference? (Calculated field is not working)..Help!!

Tks

Tks ! No it's not .