These formula's are great! One of the biggest problems I'm having is calculating the check digit for UPC-E 7 digits and UPC-E with leading 0's with would be 6 digits. Any recommendations?

Also, and this would be AMAZING, my biggest issue is check UPC-A's and UPC-E's for check digits to see if they are valid UPCs. I work with 100,000+ UPC items a day and it's really hard processing them because I have to determine which items contain check digits and which ones do not. I am willing to pay for a soluation!