Adobe Lifecycle Designer Barcodes & Binding Fields

I am creating a custom shipping form that has fields that are bound to barcodes.   When I type in the fields, the corresponding barcode prints below it.  I need the barcode to have 3 additional characters included that are not a part of what I type in the field to generate the barcode.  For instance, I may type in the field CFWY959-219752, but I need the barcode to be 12KCFWY959-219752

Any ideas on how I can accomplish this?