Average function and MSSQL Analysis services

Hi All

This should be pretty simple I think, but I can't make it work:

Using MSSql 2000 with Analysis Services I have created a cube. In this cube
I want to have a measure or calculated member that gives me the average
instead of the sum.

My data looks like this

Qty Weight
2 50
4 40
3 55

No matter how I do it I always end up with the sum (50+40+55) but what I
really want is the average (50+40+55) / 3 or preferably the weighed average
((2*50) + (4*40) + (3*55)) / (2+4+3)

How do I do this??

I'm using Excel 2000 Pivottable to present the data.

Thanks in advance


Bent