How to Make Pivot Table Sub-Total to subtract

[yfrolov]

Hello,

I consolidated 12 months "plan and actual" 2 tabs into one pivot table.
Using
Column Field: Column and
Row: Row and Page 1
Data: Sum of Values
I get 12 Months report with
Actual ###'s
Plan ###'s

Is there a way to Create a field called Difference in the Row and subtract Actual less Plan across each period.