I'm in a similar situation though in SSRS 2008.

I am interested in knowing how to write an expression that says;

iif the row_description is A then return Count(item_id)

Iif the row_description is B then return AVG(price)

iif the row_description is C then return Count of C's item_ids /iif row_description is A then Count of A's item_ids.

In other words, I need a top count to be based on a different condition than the bottom count.

what approach and functions to pursue?