Join Date: Jul 2007
Location: San Francisco/Sydney
Programs: UA 1K/MM, Hilton Diamond, Marriott Something, IHG Gold, Hertz PC, Avis PC
Posts: 8,162
Many complex itineraries can not be booked online.
Use the online tools to confirm availability on each leg as a one-way trip, and then call to get it booked as a single ticket.
As others have said, this isn't a legal 'return' trip, so will likely price out as 3 one-way trips - US->Africa, Africa->Asia, and Europe->US