Code to redirect site visitors based on origin (USA/not USA)

We have an established website and would like to add a pricing page that varies by country of origin. This is simply to display pricing and IS NOT a shopping cart. Here's the logic: -- All visitors see export pricing (page already created) -- UNLESS origin is USA, then redirect to USA pricing (page already created) We anticipate this will be done with the visitor's IP address. We do not want to use an annual-fee IP listing service since we are only filtering by the USA IPs and feel that would be a waste of money. An API to identify the country is available and can be provided. If you have a better solution we would be open to hearing it. Expected results: Code, htaccess mods, and/or PHP with all required instructions on how to incorporate into the existing web pages.