- Click Manage tab
Customization panel User Interface. 
At the Command prompt, enter cui. - In the Customize tab, Customizations In <file name> pane, click the plus sign (+) next to the Mouse Buttons node to expand the list.
- Right-click a mouse button section. Click New Button.
A new mouse button (named Buttonn) is placed at the bottom of the selected list.
- In the Command List pane, drag the command you want to add to the mouse button in the Customizations In <file name> pane.
- Click Apply.