If you suffer from hand tremors and using the mouse is difficult, then try changing the mouse speed.
To do this Press start at the bottom left of the page, go to Control Panel and click on Mouse.
Choose "Pointer Options" and reduce the pointer speed. This will reduce the movement when the mouse is shaken and make it easier to select the button you want.
It may also be helpful if the number of lines one click of the mouse wheel causes is reduced.