Accumulating cursor / gadget

I need you to design and build it. I need a cursor widget that when I point to a zip code on any website, or on the computer, it will give me amount of Miles I'm away from ithe. For example if I am located in Seattle Washington, and a point cursor to zip code to 30301 which is Atlanta, it should give me 2636 miles. If I'm driving on the road my location changes every time, and I need it to clearly calculate the amount of miles I am located from a certain zip code that I Point to.