adding check digit

I have a retail store that operates a pos system uses MS ACCESS as the database for the software. We currently use UPC's as the lookup code. For the last 2 years we have been using just the 11 digit upc, not using the last or check digit. All of our suppliers have now switched to using the check digit (12 digits). Instead of completely re-installing all of our data and losing some of the custom lookups and aliases, we would like a program to run once, that will convert all of our 11 digit upc's to 12 digits, and replace the 11 digit number with the 12 digit. I have located a script that will calculate the check digit(is free for users or developers) and have considered spending the time to learn Visual Basic to create such an application. But it may be in my best interest, both time and funds, to have a professional create such an application. If you or someone you know would be interested, please let me know, I will send more details on our system and the script. ## Deliverables Program to read 11 digit upc, calculate check digit, replace 11 digit upc with 12 digit in database