Once an item from a drop down list has been selected, I would like the sheet to be able to deduct the item selected from my stocklist

I am using google sheets to keep track of my stock in my frozen food business.

On my Sales page I have a dropdown list of all my products. I am wondering if its possible once i click on a product on the sales page, how can i make it decuct that same product from my stock list automatically?

wondering if a macro would be required however i am very new to these.