GREAT QUESTION!!! I really like it....
Lets take a look here.. If you roughly move your mouse 4 inches, everytime you use it. And We will say you are on the computer, roughly 4 hours a day... And in that 4 hours, we will say you move the mouse 200 times... thats roughly 800 inches a day X 365 days X 3 (years) = 876,000 inches... divided by 63,360 inches in a mile...would give you a rough estimate of 13.8 MILES!!!!!!!!!!!!!!
(use this equation of sorts to plug in your estimates!)
I hope this helps...