to add conditional Subtotals formula in a pivot table

There are positive and negative number in a data sheet, when create a pivot table, under the subtotals, the numbers are added and hence the negative numbers are deducted from positive and net amount is shown.

I require total of only positive numbers in subtotals, however need to show the negative numbers in the body.

Currently I am doing it manually by using "=sumif(range, ">0")" formula in subtotals after value pasting the pivot table. With any change I need to the same exercise over and again.

Attached is the sample file, with desired result in right side.

Thanks in advance.

Thank you for the prompt response.
The problem in having an other column with positive numbers only is that, in the body the negative numbers will not be shown.

Ok...

Thanks again.