I wish I could use a finance rule. The event launching this logic is the click of the Report button in a Cube View. I think that limits me to a Cube View Extender.
The report button is definitely Cube View Extender territory. Nothing comes to my mind immediately how you would accomplish that in a CV-Extender as we've not done much more than the basic logo or color change type stuff. That doesn't mean its not possible though. Maybe others have thoughts here?
Else, my next thought would be: is there another way to achieve a similar result via a slightly different avenue. Is the expansion different from what is displayed on screen? Or is it that what will be displayed is based on the cell intersection a user has selected? There might be some ways to do this with the new TreeExpansionLevel feature from 7.3; or by using Linked Cube View / Dashboard Drilldowns
