calculating variance

[semsel]

I have Item, Item description as groups and then Qty, Amount and Avg Price in the Rows and fiscal year in the columns ( 2011 and 2012).

I want to calculate the variance for the Avg price in  the two years.
for eg:

Avg(2012) - Avg(2011) / Avg (2011)

Can you please help me ?

[blom0344]

Relational or Dimensional model/package ?