Africa - Flights into SA

My wife and I are considering visiting SA next spring. I was wondering if anyone with experience could help me figure out the cheapest way to fly into JNB or CPT. We live in Birmingham, AL, could easily drive to ATL, and would be willing to get to SA via Europe and could even spend a day at our layover stop.

I guess the same question, a different way, is: does anyone know of a website that allows you to "back into" a destination? The idea would be I plug in my final destination, then look for the cheapest flights into that destination, then look for the cheapest flights into that destination, etc. I understand that sites like Kayak, etc search for cheap flights but it seems like this would be a slightly different way of finding the cheapest flight.

Thanks!

There are direct flights to JNB or CPT from many points in Europe on several carriers as well as direct flights to JNB from JFK and IAD on South African Airlines. Kayak will also let you look at layover airports in the bottom of the left screen which could also be a method of finding where you may transit.

Malaysia Airlines flies from South America, i think EZE to CPT and may be cheaper.

In July-Aug 2010, my two sons did a RT ATL-JNB with Delta. It was direct and cheap.
Between JNB-CPT use one of the South African LCC flights or take the train in posh(er) sleeper (berth) and see the Karoo and ... as you speed by on the electric train.
Look at the following search engine for results: matrix.itasoftware.com