Scanners typically operate in "Keyboard emulation mode" which means your computer thinks a very fast typist entered the scanned data one keystroke at a time. OnObjectModify will thus be tripped once for each and every character input from the barcode scanner--just as though you had typed the infor from the barcode instead of scanning it.
If you want the script to be performed automatically each time that the barcode is scanned, configure your scanner to append a return, enter or tab character to the end of the scanned data and set the field receiveing the scanned data's behavior to exit the field when that particular key is pressed. Then you can use OnObjectSave or OnObjectExit to automatically run the script immediately after scanning a bar code.
Hot diggity dog, Phil...I'm big time now!
Thanks...again & again...etc...