Take a look at the following tutorial - it gives a step by step description
of how to do this including screen shots. The basic gist is that you create
a custom tool bar, then in the Customize dialog, click the Commands tab and
drag a "Custom" button on to the new tool bar. (Category: File, Custom
should be at the top of the list). Then right click on the new button and
select properties. In addition to setting the display properties of the new
button you can specify an OnAction which can be either a Macro (not my
preference) or a function.
Check out the link for the step by step instructions:
http://www.jamiessoftware.tk/articles/menubars.html
