Big problem in a report

Hi,

I have the following sales movements in a InfoCube:

(customer)(product group)(value)

X - A - 10

X - A - 5

X - B - 5

X - C - 1

Y - A - 2

Y - C - 1

Z - C - 1

I need to create a report below:

(product group) (number of customers) (billing value)

A - 2 (X,Y) - 24

B - 1 (X) - 21

C - 3 (X,Y,Z) - 25

My difficult is crate the column "billing value" because in this column enter only the value for the product group in the same line. Instead I need the total billing value for the customers.

thanks and regards