Adding new calculated/column field to pivot table

I generated a pivot table using financial data for clients/by year/by sales rep. The table successfully calculated the Individual totals by rep by year as well as the grand totals by rep and by year. The only grand total it did not calculate is the overall grand total by client. I know I can simply generate a sum field/cell manually, but am unable to label that column as the grand total. How can I get this grand total to calculate and have it become part of the pivot table itself?

Thank you.