The ChronoTrack Live registration process restricts entrants to 1 coupon code per entrant.
However, depending on how the Race Organizer set up their coupons and discounts, you may be able to use a coupon code on a race that already offers a special discount to the base price such as a Military or EMS discount.
For more information on an Event's coupon and discount policy, contact the Event Organizer directly from the Event's Web Page.