Google Sheets: remaining quantity formula???

Hi,
I have on order list excel table that constantly updates, once a customer orders sth. And i have so far managed to make a function that calculates the total amount of products that has been ordered. What I would like now to add, is a field showing me the "remaining quantity to produce/ship".

In order to do that i need as well a field "shipped" with the option to write "YES" once i have shipped an order. And when i write yes, then from the TOTAL products, we subtract the amount it has been shipped, aka "remaining quantity to produce/ship".

I tried many formulas but with no success. Please help!

Best
Denis