Sorry about that, Pegi. I sent the 2nd file again via email and I believe you'll see how inventory balance is automatically maintained merely by creation of "consumption" transaction records. The barcode scanning doesn't "cause" the adjustment per se: it just makes data entry more reliable and faster. You can accomplish exactly the same adjustment to inventory balance by typing in the consumption record. The keys to automatic updating are the master file/transaction file combo, running totals, and link/relationship on the item number value used in both files (which happens to be a barcode).
Hope that helps.