Average calculation in Parent node

Dear Experts,

I have following report

XYZ

                                         Expense      % increase        Forecaster values

                                           2012                 2012                        2012

      Account 001                  10                    1.05                         10.5       

      Account 002                   20                    1.05                          21

Account 000                         30                     2.10                          63

>I have a dimension member formula on (Forecaster values category that the value will be Expense* % increase)

The problem i am facing is that when i gives the value of 1.05 in each base level account 001 and 002 it automatically sum up (1.05+1.05) 2.10 in to account 000 member and apply the same formula and gives 63.

I want that on the Account member the value remain 1.05 and calculation will be performed as following 30*1.05=31.5

> As i cant take 1.05 on Account 000 because its not a base member How the problem can be solved

I Want Average calculation in Parent node rather than add

Regards