I offer gift certificates that can be purchased on my site that can be applied towards any item. They are set up for $50, $100 & $500 increments that can be combined or used seperately. I tried setting up the discount code but it will only take one code, where I need more options for each amount. Is this possible? Also, since I already have buttons for each item set up is there a way to change all of them at once or would it have to be done individually?