If I'm reading this correctly, I think this will give you what you are looking for:
1. Modify the Range Scale formula to include your overlay variable as your By group variable and then add the Excluded() argument. See below example from the Semiconductor Capability sample data table using the NPN1 column with SITE as the by variable :
2. Use the Global Data Filter to filter the NPN1 (or your Y) variable. Be sure to check the "Show" and "Include" boxes on the Global Filter. This will change the Range Scaled column data result to reflect the filtered range of your Y variable.
The Local Data Filter will not work since you need the filter to work on the table and the graph.
Hope that helps.
-Jerry