Mouse Button AssignmentsKeyCreator \ Tools \ Customize \ Commands \ Mouse-Button-Assignments
Mouse buttons can be assigned using the same method by which shortcut keys are assigned. The button types are listed in the Mouse Buttons section, at the bottom right of the Commands tab. Choose a function from the Categories/Buttons interface at the top of the dialog, then select the mouse button that you wish to assign to that function.
The text in the center will tell you if that button is currently assigned to another function. You can then choose to override the earlier setting if you wish.
To apply the setting, press the Assign Key button at the bottom of the dialog. The available mouse buttons are:
Notes about Mouse Button Assignments