Inventory - Add OTY and substract OTY with Barcode scanner

Dear SS Team,

since i am still quite new, i need your help. I would like to manage our inventory with smartsheet, I would like to do it with the barcode scanner. how can I create a form that adds / subtracts from the inventory and then returns to the current inventory qty. that should work the next time you enter other vlues(oty) as well. A sample sheet/form would be vary helpfull. Many thanks in advance.