Adding column by calculating values from previous columns

[suthashiniv]

Hi,

I would like to add to new column to my pivot table.

Currently i have 3 dimensions. I created an expression, 'Combined Average' which is an average of the column M1 and R1 per Year.

Now i need to create another expression, which is a comparison of the combined average. For Example, in the table below, i need to have another column beside the 2nd Combined Average column, called "Comparison" which is (6.06-6.54)/6.54.

I will have to do this comparison for the remaining columns as well. How do i add this expression to use the values from the Combined Average expression?

I have attached the file for reference.   

	AY	May 11 - Oct 11	May 11 - Oct 11	May 11 - Oct 11	Nov 11 - Apr 12	Nov 11 - Apr 12	Nov 11 - Apr 12
Qns	Type	M1	R1	Combined Average	M1	R1	Combined Average
Q1		6.30	6.78	6.54	5.65	6.47	6.06
Q2		6.30	6.86	6.58	5.90	6.63	6.27
Q3		6.50	7.05	6.77	5.93	6.82	6.37
Q4		6.50	7.00	6.75	6.00	6.71	6.36
Q5		6.13	6.62	6.37	5.59	6.24	5.92