I was plan to scan the barcode and send the bar ID into specific excel cell inside the SD card
What you ask is not possible.However, you may want to look into saving your excel sheet into a comma delimited file,
I submit I am older that you are
I think it was a magnetic core or drum memory or something , right ?
Is the Commodore 64 a uC or is it a computer with an OS ? (I don't know so I' asking)Does it have more memory than an arduino ? Can it run Excel (I haven't seen anyone do that with an arduino.