Adding a New Quicktag
Open the quicktags.js file in the wp-admin folder of your WordPress installation. Insert your version of the following into the list of buttons where you want your own quicktag button to appear.
edButtons[edButtons.length] =
new edButton('ed_name' // the name used with the setup
,'name' // the name that will be displayed on the quicktags bar in the Admin section
,'<tagopen>' // the opening tag the button will insert
,'<closetag>' // the closing tag the button will insert
,'x' // the accesskey to activate this button from the keyboard
);