Change the sum function to subtraction
Today when a pivot table is made and we ask you to add a total on some level, the excel adds. You could have an option to change the sum function to subtraction. For exemple I would like to substraction two lines, today I made de pivot tables, copy and paste the table and I add a substracion at the line subtotal.
Kenneth Barber commented
What if you have more than 2 lines? What if the order of the lines changes?
Subtraction is just the addition of negative numbers. In your data source, add a new column that keeps the minuends the same and negates the subtrahends. Use this new column in your PivotTable and summarize with Sum.