We have set up the ability to edit the discount code on your own.
Goto the bottom of the "Miscellaneous Charges" configuration section under "Advanced" level, and you will see your current discount code inthe format actually used by the shopping cart.
If you follow the format given at: http://www.netstores.com/help/param20.htm#DISTAB you can change the discount codes used by your store.
If you make changes, be sure to click on the "Save Changes" button onthe button of the page.