You could create a combine or shared axis chart, some LOD, a parameter, and play around with context filters
Let me show you one example using the Global SuperStore Dataset http://www.tableau.com/sites/default/files/training/global_superstore.zip
I'll create a view to show the Top 1 Region by Sales, Avg sales per region and the Sales for the selected Region base on a parameter
Create a parameter base on Region dimension
Sales for the selected region
LOD for Top 1 Region by Sales
LOD for Avg Sales per Region
NOTE: The YEAR filter and CATEGORY filter are added to the context so the LOD calcs update with that selection.
Attached .twbx file for reference
Let me know if this helps!
Book1.twbx 6.9 MB