Tweak to formula in Sheet3, in line:
In O2:
=IF(MAX(C2:N2)<300,"",INDEX($C$1:$N$1,MATCH(300,C2 :N2,1)+1))

Make it as

In O2:
=IF(MAX(C2:N2)<300,"",IF(ISNUMBER(MATCH(300,C2:N2, 0)),INDEX($C$1:$N$1,MATCH(300,C2:N2,0)),INDEX($C$1 :$N$1,MATCH(300,C2:N2,1)+1)))

Revised sample available at:
http://savefile.com/files/2697802
AutoCalc_AgentsCommissions_2.xls
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Max
Singapore
http://savefile.com/projects/236895
xdemechanik
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