Formula to copy a number from a cell and make the number fixed

G'day all,
I am about to do my end of financial year stock take using a barcode scanner. All this works fine, the issue is when I enter the stock count for the item in column A3 that has just been scanned I would like that number to automatically appear in the stock count cell next to that product that the barcode represents in the list. Then when I move the cursor back from A3 to the bar code scan cell again, scan another number hit enter and the cursor automatically moves left and a new stock count for that product is entered, the problem is that when you enter a new stock count number in cell A3 the previous stock count amount goes back to zero or n/a or false etc. What formula could I use to place the stock count amount in the correct cell next to the selected barcode item in the list and It permanently stays there. I have attached part of the price list so you can see.
Any help appreciated
Cheers
Grant

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