A keyboard accelerator allows you to select a menu command or button by pressing ALT+<single letter>. For example, to open the Edit menu, press ALT+E.
If the button or menu command you want to change is on a toolbar, make sure the toolbar is visible.
How?
On the Tools menu, click Customize.
With the Customize dialog box open, do one of the following:
Assign or change a toolbar button's keyboard accelerator
Click the button on the toolbar.
In the Customize dialog box, click Modify Selection.
In the Name box on the shortcut menu, type a name for the toolbar with an ampersand (&) before the letter that you want as the keyboard accelerator.
Press ENTER.
Assign or change a menu command's keyboard accelerator
Click the menu name on the menu bar or toolbar.
Click the menu command.
In the Customize dialog box, click Modify Selection.
In the Name box on the shortcut menu, type a name for the menu with an ampersand (&) before the letter that you want as the keyboard accelerator.
Press ENTER.
In the Customize dialog box, click Close.