I am holding a round trip reservation from LAX to CMH (going through ORD, returning through DEN); I want to book my husband on the same flights now. But when I try to do this on united.com, I can't see an option to book the same return flights as I have. If I enter departure cities individually, then I can book each leg (CMH to DEN; DEN to LAX) separately. So it doesn't seem as if the flights are sold out or unavailable.

Is there anyway to book this flight short of calling United? (I can't see it on any other site, e.g., Kayak, Expedia) either.