The effect of a YES/NO variable on the sum of another column

[Jabbs]

Hello
I have return form for my inventory app.
I record every return - before receiving the goods back.
I have a column. Goods received? YES / NO
with the NO option - the condition of the item remains the same.
when I receive a return from a customer (YES value) , I would like the sum of available items to increase by the number of items returned.
How can I do that ?
right now AVAILABLE column formula looks like this:
SUM([Returns][Pieces]) + [Available] + SUM([Purchases][Pieces]) -SUM([Sell][Pieces])

I just want to add YES value RETURNS.