In Excel 2007, you can add controls to almost every context menu with VBA code. However, it is not possible to change some context menus such as the Shapes and Picture context menu with VBA. In addition, it is not possible to change context menus with RibbonX.
In excel 2010 it seems you cannot modify the shapes context menus with VBA (just like in excel 2007) but you can with RibbonX
[FONT="]In Excel 2010, you can add controls to almost every context menu with VBA code. The same restrictions for changing some context menus with VBA as in Excel 2007. Additionally, you can add buttons and menus to every context menu with RibbonX but if you want to disable or re-purpose controls, you may not be able to find the correct IDs (idMso).[/FONT]