The Boeing planning software I have cannot specify a runway elevation - I have to use an actual runway, but it would take me forever to go through the library of airfields to find one suitably high to run your calculation. (It doesn’t have Nairobi).
Best I can offer in the time available is :
737-400, ZFW 32700 kg
Runway elevation 2316’
TORA 2400m
10kt headwind
15 deg C
1013 mB
Max take-off weight under these conditions = 59700 kg
So max payload possible will be 59700 - 32700 - 10000 = 17000 kg.
Hope this helps.