Customizing Context Menus in Office 2010

In Office 2010, you can customize built-in context menus just as you can the other components of the Ribbon UI.

Prior to Microsoft Office 2010, the only way to customize context (right-click) menus in the Microsoft Office Fluent Ribbon user interface (UI) was by using CommandBars solutions.

Link: Customizing Context Menus in Office 2010