Rather than searching by image
It's surely better to convert all the barcodes you have to their numerical equivalent using some sort of barcode-number conversion, then search the number table via a simple database query. Less potential for error than matching images I think. Have you just got the barcodes as images, or are they numbers written with a barcode font?

Do you know what standard you're using for the barcodes? I'll look for some software to convert them to numbers, we write our own in house so I may even be able to rip that off and knock you something up, although it sounds like you're after something subtly different...

PS - @ Legless - someone of your IT fu should surely know that the correct format should be .png, or at a stretch .gif, not .jpg! :P

Edit: Just seen your reply posted at the same time as mine, I will have a bit of a think now I've got more info.
(Son of Sam-i-am We're all as mad as hatters here, Wed 4 Feb 2009, 11:29, Reply)