I want to use Avg(<Set>, <Numeric Expression>) to calculate the average on rows.And how to calculate it dynamically when members on rows change.

Jpivot1.8+Mondrian3.4.1

like:

Sales Cost
USA 100 80
Canada 60 50
France 70 60
Italy 40 50
China 80 60
------------------------------------
Average 70 60

When I choose USA,Canada and France

Sales Cost
USA 100 80
Canada 60 50
France 70 60
------------------------------------
Average 76.6 63.3