[Koha] Playing a sound file with bad barcodes

We've trained our staff to look at the screen as they're checking materials in & out, but every now & then circ staff miss when a barcode is misread. This means that an item is either not properly checked in or not properly checked out. A neat enhancement would be to have Koha play a sound whenever this happens. In the meantime, has anyone used a Greasemonkey script or the like for this purpose? Text of the error messages is as follows: No Item with barcode The barcode was not found Other ideas I may have overlooked? Thanks, Cab Vinton, Director Sanbornton Public Library Sanbornton, NH "Politeness and consideration for others is like investing pennies and getting dollars back." Thomas Sowell