Dynamic SUM Cell Range

Hello,

I need to create a dynamic SUM that will accommodate column members changing (added or removed) and the cell (row) that contains this calculation will shift up and down the report because the users will be selecting different hierarchies and drill down.

So cell D280 should go all the way across to the right as the column members expand and collapse. Also, when the hierarchy changes this calculation could move to cell D80 (as an example). How can this be accomplished? I got pretty close using a local member formula but couldn't get a consist result.