Webi - Multiply row values and aggregate

Hi,

I am trying to do some report level calculation in which I need to multiple two measures and then aggregate the values.

Here is an example:

Region     City     Unit Price     Qty Sold     Rev

A     C1     10     2     20

A     C2     20     3     60

C     C2     30     4     120

                    200

Table above has Unit price & Qty sold for each region and city.

I calculated Rev by Unit price * Qty sold, and also got sum of rev as 200.

But when I try to show the Rev at region level I dont get the right figures:

Region     What I need     What I get

A     80     150

C     120     120

     200     270

For Region A I shd get 80 ((102)+(203)) and not 150 (30*5).

can someone provide suggestions to get this to work...

I've tried using some context but no luck so far..