Addition across rows & columns

Hi all,

I am new to Business Objects so please bear with me. I am using a cross tab in Web intelligence.

I want to compute sum across rows & columns & divide the cells with this sum. foreg.

interval1 interval2

Count Count Sum

A 1 3 4

B 2 3 5

Sum 3 6

Now I want to first obtain sum across column & rows. and then divide cells in interval1 with 3 & in interval2 with 6

Thanks in advance.