how to delete Discount Coupons from customer?

I've just delete an order by a customer, because he want another type of product. But when he entered his new order did not have access to discount voucher, because already collected. How can I delete discount coupon from a customer's account?

I'd just create a new one for one time use.

perhaps I was not very clear. Deleting the customers order I want that the customer can still use the voucher.

To use the same voucher code you'd have to modify the database, which I wouldn't be the person to guide you through... I mainly suggested creating a new voucher/coupon code for this isolated incident because the work-load would be less than figured out how to re-allow a customer to use a code they already used, outside of them creating a new account altogether.