Well, I finally figured it out myself. At least, I figured out a way to get what I need. It may not be the best way, but it works.

For each dimension I want to see this "ratio" for, I need to create a calculated measure (since I cannot figure out how to get it to default to the dimension being browsed).

For instance, if the dimension being browsed is Store…the ratio of how a store's avg order amount measures up to the avg order amount across all stores could be determined with the following MDX:

([Measures].[Avg Order Amt])/(([Measures].[Avg Order Amt]),Store.Parent)

Sheesh.

Someone please let me know if there is some way to parameterize that Store.Parent part to be CurrentDimension.Parent or something of that nature.

Mindy