Barcode Scanner - number of identical scans to increase quantity

Hi, Here is my problem.

I have 3 shops in edinburgh all selling the same stock. I have just finnished doing a stock take of 1 shop and have purchased a usb barcode scanner to speed up the other 2 shops.

All the items in the first shop have been manually added to the excel spreadsheet, and barcodes scanned for each item.

What i want is; to be able to scan a barcode, excel to find that barcode in the spreadsheet and add 1 to the quantity column for that row.

I hope that makes sense...i have tried google and i just dont have the lingo.

Any help would be most appreciated.

Thanks!

How does the data get from the scanner to the spreadsheet?

Once the data is in your spreadsheet, it can be done with a little vba, but I'm curious about the process before that point. Also, can you load a sample workbook with some of the data so the incredibly awesome people here can have a better idea about the structure?
Thanks!

Did you get any software with the scanner?
Whats it called?
Is it to add data to Excel etc?

OR did you get Excel AddIn for this?

What the scanner (make/ model)

Hi, the scanner is plug and play. it scans the barcode and pastes the numerical data into the box selected on excel or any other text input area.
it also puts 'enter' at the end of the line so that it drops to the next box.

for example: i will scan 3 barcodes in here...

671860013426
00735452
15G351042100

Attached is the spreadsheet

I think I'm missing something - I don't see any barcodes in the SKU column at all.
Also, if a barcode is scanned, and NOT found on your spreadsheet, should it add that barcode and descriptive info?