You can do it using the instructions from Chip Pearson's site:
http://cpearson.com/excel/vbe.aspx

But I wouldn't attempt it.

Instead, I'd separate the date into a normal workbook and the code into an addin
(*.xla).  Then you can just update the addin and redistribute that whenever the
code changed.

You may have to give the users a way to run those procedures.

For additions to the worksheet menu bar, I really like the way John Walkenbach
does it in his menumaker workbook:
http://j-walk.com/ss/excel/tips/tip53.htm

Here's how I do it when I want a toolbar:
http://www.contextures.com/xlToolbar02.html
(from Debra Dalgleish's site)

And if you use xl2007:

If you want to learn about modifying the ribbon, you can start at Ron de Bruin's
site:
http://www.rondebruin.nl/ribbon.htm
http://www.rondebruin.nl/qat.htm  -- For macros for all workbooks (saved as an
addin)
or
http://www.rondebruin.nl/2007addin.htm

In xl2007, those toolbars and menu modifications will show up under the addins.