I know that. But I want only 1 code to be used 1 time. Suppose: I have two products ‘Example 1 Month’ and ‘Example (its 1 month/2month/6month) variation/variable). I want to add a key like Example 1 month and variable product for 1 month. And no matter where the customer orders the 1 month product, a key will be delivered only once.