Add a button to tinyMCE editor on Custom Post Type

How do I go about adding a simple button to tinymce on the default editor area of my new Custom Post Type?

I’d like the button, when clicked, to ask for a text value. The script should then lowercase the input and replace spaces with hyphens, and insert [glossary=value-entered] into the editor.

Thanks in advance,

Check out this tutorial on Pro Blog Design: http://www.problogdesign.com/wordpress/user-friendly-short-codes-with-tinymce/