Is there a way to remotely authorize any MAC address or name with a voucher code? this would work well payment button on the portal page for automated payment.

I've had seniors were I'm not available then someone wanted to purchase a voucher, but I rather grant them access the network with a voucher than me sending the code to them(for fear or shearing) or just authorizing them by clicking in the clients list tab? 

I've authorize a few connections via the clients tab then forgot to unauthorize them after their time expired.