Display phone number based on referer URL

We need to display a unique phone number on all website pages based on what website a visitor arrives from or based on a unique URL we can provide with our paid advertising on others websites. The phone number displayed must follow visitors from page to page throughout their session. Not used for affialite tracking. Not used on secure pages. Need approx 90% accuracy or better. Using cookies, sessions, http_referals, or other means all acceptable. Landing page may vary and will not always be [login to view URL] but will always be within our domain such as [login to view URL] Fancy user interface not required. Statistics, reports, data storage not required. Simple to deploy and modify are main priorities. Users will not have programming abilities. 1) Ideal solution: Phone number controlled by URL addon like [login to view URL] We can give this unique URL to advertsers and be certain referals from their site will see a phone number we choose. 2) Acceptable solution: Phone number controlled by base URL of http_referer like this: If from [login to view URL] - 800-123-4567 If from [login to view URL] - 800-456-8910 3) Other solutions welcomed. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Deliverables must be in ready-to-run condition, as follows (depending on the nature of the deliverables): a) For web sites or other server-side deliverables intended to only ever exist in one place in the Buyer's environment--Deliverables must be installed by the Seller in ready-to-run condition in the Buyer's environment. b) For all others including desktop software or software the buyer intends to distribute: A software installation package that will install the software in ready-to-run condition on the platform(s) specified in this bid request. 3) All deliverables will be considered "work made for hire" under U.S. Copyright law. Buyer will receive exclusive and complete copyrights to all work purchased. (No GPL, GNU, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the buyer on the site per the coder's Seller Legal Agreement). ## Platform This solution will be incorporated into an HTML site published via FrontPage with server extensions. Server is Linux.