We have a site to sell charity lottery tickets. All sales must take place by telephone. We drive traffic to the site by email campaigns and online advertising. We track performance of these efforts with different phone numbers. We display the phone number to call on our site as both an image (site-wide banner graphic) and as text (on how to order page). We are looking for a way to display different numbers to visitors based on their origin. For example, if arrived via email campaign, show this number for duration of visitor session, else if from online banner for site A, show this number, etc. It is important that the number displayed persist for the entire session, either from a cookie or passing of session variables. We use Google analytics to track our links, so all inbound links will be tagged with Google analytics URL parameters that could be used to determine number to display. If not parameters are present, a default number should be displayed. 8-10 number options in total.
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Site is primarily HTML with some ASP to have include files. MS SQL server is available, but if a non-database option is available, that would be preferable.