Address Validation using UPS & USPS API with Visual Foxpro

Have over 60 customer location in all 50 states of the United States including the islands territories. In each of the customer location there are orders that are produce by the customer. The customer electronically send the customer order for shipping. This require that the customer validate there address. Customer Address Validation must happen at the Street, City, State, Zip Code level. Looking at two possiblity for validating the customer order. First propose way is to validate it on the customer client machine before the order is upload. Secondly, to take the customering existing data and clean up the data and send updated list to each customer site (Over 60 site). Note: We have a master table of all of the customer that the customer have ship order to. Conclusion this should be done with the UPS or USPS (United State Postal Service) API. Again not sure what would be the best way to do this process. The Application that is on the client machine in the different state is a Visual Foxpro Application. We are the people who support and develop the Visual FoxPro Application that the user in the field use to create their orders. Looking for someone who has experience working with Visual FoxPro and these API that UPS, Fedex and USPS (United State Postal Service) . These company say that they provide these API to help customer validate Address (at the Street, City, State and Zip Code LEVEL.) I can send you the link that we have been looking at with Validation API(UPS, FedeX and USPS (United State Postal Service)