Subtracting one sum of counts from another sum of counts in a pivot table

Hi
very much would appreciate assistance.
i have a pivot table with the sum of the count of product LL under the row being the outcome of WIN and the sum of the count of product LL under the under the row which is outcome of LOSS.
i have attached what i mean here

i am trying to create a new field column that creates the calculation of A. the count of LL of WINS which is 7 subtraced by B. the count of LL of LOSS which is 1 to = a new "result" filed that should obviously show 6

unfortunately no success with this despite much searching through the web over a few days , can anyone help with this - it would be greatly appreciated.

thanks

steve r