Your closest option is to fly from Durban's King Shaka Airport to Lanseria Airport.
There are no airlines operating flights from Durban to Pretoria (Wonderboom Airport, PRY). Interlink Airlines, which was operating flights on the route, went into provisional liquidation on the 23rd Feb 2010. Hopefully, when one of the new airlines starts up, they'll restart the route (new airlines wanting to start operations in South Africa are fastjet, FlySafair, 1time Airlines and Skywise Airline).
The driving distance between Durban and Pretoria is some 618km.
Translux & Intercape intercity coaches operate bus trips from Durban to Pretoria.