I have a set of data that relates to item sales over time by store.

In a table (Below) I have a "% of total" column that breaks down by pane as I flow through a product heirarchy.

I have managed to create the avg "Sales_Value" column called TEST (copy), using a WINDOW_AVG calc.

My problem is that I can't do the same for the first column which is a table calc already. I have tried to apply a window_avg again but all I get is 20% for all rows.

Any thoughts from the geniuses out there?