Hi Vadim,
I tried your solution above, but I still get the sum in the parents not the average !
2014.01 2014.02 2014.03 2014.Q1
Area 12 13 10 35
ProductivityPerHectare 0,9166667 0,7692308 1,2 2,8858975
Productivity 11,0000004 10,0000004 12 33,0000008
Regards
Maha