Expression to avoid entering of the barcode not from the given list

[NNN]

Hi, I have a field for barcode scanning (I use a usb scanner). I need to prevent a user from entering a barcode which is not in the list (column Barcode, Table ‘Items’). I tried Data Validity (Valid if=), but it gives me a drop-down list in the field for barcode scanner.
Could you show me the direction, please?