I am currently working on adding a discount for an existing order which is not invoiced yet in Magento admin panel. To do that I thought it is better to use Coupon codes. What I am trying to do is adding a coupon code for an existing order to make a discount on that order.
Till now I have added the coupon code input box into Order control panel. I need to connect that field with the Coupon controller and add a new function to add coupon code for an existing order. Is this the correct thing to do to make a discount on an existing order or is there a better way to do that? Is there anyone who can guide me to accomplish that?