Have you ever considered of mousing ambidextrously?

I think that you may have some other issues if your hand is tired or in pain at the end of the day. While you have created a program that is useful, it does not address the problem that you are having. If your hand is that tired at the end of the day, you are not sitting properly, and your workstation is not set up correctly. I recommend that you take this issue to your superiors and let them know about it. The reason that you should inform them is so that they can get your area set up to prevent a cumulative trauma disorder, such as carpal tunnel syndrome, or other repetitive stress disorders. Also, if you don't wan to change your setup much, you could consider going to a trackball mouse.

Have you ever had formal piano, classical, or typist training? I have applied some of the technique to mouse and keyboard and find it saves much pain. It may be worth the time to train yourself how to stay relaxed and not overexert your fingers.

Get a SpacePilot

You and justgofirst are correct. Sometimes less is more. The more crap on a mouse, the more movements necessary. Get simple and get in the right position and relax.

When I started having some wrist soreness after about 5 years of CAD work, I simply switched which hand I used for the mouse. It took a little time to get used to the new hand, but not too much.

Eventually, I made it my standard practice to use my left hand for the mouse when I am at work, and then my right hand when I am at home.

An alternative is to occasionally switch to a different type of input device, such as a track ball or digitizing pad. The key issue is change, not that one is better than another.

Joe Dunfee

I use a standard mouse on the left and a trackman wheel mouse on the right. It makes a difference at the end of the day. The mouse does about 20% and the wheel the other 80% of mousing. Another thing that helps is using lots of shortcut keys on the keyboard, instead of point and clicking.

peace, Miles