I have and old logitec track ball that I have used extensively in sketchup and in panning and orbiting quickly the scroll wheel that you can push like a button is indespensible to me. This trackball is 15 years old and not working well any more and using only my thumb to control the small ball is aggravating my carpal tunnel to a point that is no longer acceptable. Does anyone have any suggestions for a replacement with a large ball I can control with my whole hand that takes advantages of the panning and orbiting shortcuts in an efficient manner. I have seen many intriguing and very expensive options but the price forbids just trying one out.