Welcome to the Board!
You're really not giving a whole lot to go on. Do you want to reassign CTRL+A to a code shortcut? If so I'd consider using an unreserved shortcut, otherwise CTRL+A won't work.
There are free barcode fonts you can use to create barcodes from a string: http://www.barcodesinc.com/free-barcode-font/
If you post back with more details it'll help.
Is there a way to convert CTRL A in excel so that the output is a 128 bar code that is printable in excel?