Return value from one cell IF criteria met in another cell with Math Operation

Every time I think I'm getting good at Excel, I realize that I'm not.

I'm not sure where to even start with this one...Not sure what formula to even use.

I input data into Sheet1 line by line. I input part numbers and the respective quantity.

I want to use Sheet 2 to keep track of the Purchase Order balance. I created a simplified example below for reference.

I need a formula for Sheet2 C3 that will keep a running balance. It needs to take Sheet2 B3 minus the quantity in Sheet 1 B:B if the value in Column A equals an exact part number.

Is this even possible?



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