I am trying to book a round trip flight for two people on alaskaair.com, using my $99 companion fare and a customer care e-certificate, but I can only enter one discount code when I try to purchase. I don't want to waste the companion fare by booking a one-way ticket for the same price as a round trip, and then using my e-certificate for the return (booked as a separate one-way trip).
Does anybody have a trick for using both discount codes, or am I stuck choosing only one of the two?