193587 Revise script

I had a project done awhile back that calculates distances/rates for my auto transport sites. The problem is that the programmer used longitude and latitude for the calculation of distance. That leaves a great variance between points. For example, from the border of Il and Ia to Denver, it shows 600+ miles for an 804 mile trip. To San Diego which is 2100 miles, it shows 1600 miles. This makes the script useless. When I brought the problem up to the programmer, I was met with silence and no solution. You can look him up as the winning programmer on my past projects to protect youself from this guy. I had already put up his review, unfortunately, before the faux paus was discovered. Anyway, I need a rework of the distance calculation with a formula that will be at least close to the distance traveled. It will need to be loaded onto two of my sites. It will need to integrate with the pricing formula script that deciphers mileage/price based on the changing prices that we input from time to time. Thanks in advance.