Grand total in Pivot-Table
 

I have a number of rows of data in a pivot table with subtotals and a grand
total. The subtotals are summarized by Average in "Field settings". For grand
total I would like to have a sum of all the subtotal averages.

However, when I choose to summarize by Average in "Field settings" the grand
total is the average of all the rows.

Is there any way I can change the grand total to be the sum of all the
subtotal averages.