Help with barcodes

Hi,

I was wondering if someone is able to help. I currently have an application that ships orders on our email system when a barcode is scanned. This has been working fine and was set up for a six digit code. In which I was able to detect that after six characters the input from the scanner is complete.
My problem is that we now wish to process orders that have a variable length barcode. Is their barcodes with a start and end check character? I thought that this would possibly be a better way to do this?

Any thoughts, ideas or suggestions are appreciated.

Regards,

Ross