Make a tiny small program in excel

Is it possible to make a small program in excel? Or more specifically excels duplicate OpenOffice Calc?

I want to create an inventory system so my barcode scanner will enter the barcode and hit return. Then to have a script that runs that barcode and if found in column C add 1 quantity to the quantity column D.

Basically to cells on that would -1 every time it matches a barcode and one that would +1 to the quantity.

I don't want to enter the barcodes in multiple cells I want to select the cell, scan it(which would enter the barcode and hit return), then for it to search and add quantity automatically. And stay in this box so I can scan another without changing anything. Thanks a lot God Bless You All.