Africa - Lusaka to JNB

We have a flight arriving in Lusaka from Mfuwe, Zambia at 1750 on Proflight. We'd like to catch the South African Air flight to JNB at 1820.

Has anyone been through Lasaka? Is this an impossible connection?

Thank you for your help!

Unless you already have a boarding pass it sounds unlikely, not to mention forbidden:
http://www.flysaa.com/Journeys/cms/ZA/essentialInfo/_categories/essentialinfo/closureTimes.html#