(I guess it is not possible, but I might be overlooking something simple)
Is it possible to define a calculated member that does some calculation at the lowest level and have the result aggregated.
For example:
In the Builder, you define a member [measures].[calc] as [measures].[amount] X [measures].[count], and have the product only calculated at the lowest level and then its result aggregated over all dimensions.
A quick and easy answer, not yet