1. Click Manage tab Customization panel User Interface. Find
2. In the Customize tab, Customizations In <file name pane, click the plus sign (+) next to the Mouse Buttons node to expand the list.
3. Right-click a mouse button section. Click New Button.
   

   A new mouse button (named Button n) is placed at the bottom of the selected list.

4. In the Command List pane, drag the command you want to add to the mouse button in
   the Customizations In <file name pane.
   
5. Click Apply.

Learning AutoCad