title: Set coupon code used for customer in Magento
body: <p>I'm integrating a system with Magento.</p>
  
  <p>When I create an order, if my non-Magento system indicates the order does have a coupon I would like to mark the coupon code as "used" for that customer, so the next time he tries to use it, Magento will know that customer already used it.</p>
  
  <p>How can I accomplish this?</p>