Pivot Table -- Add column to average Grand Total

[Guest]

I have a pivot that someone wants to get the average of the Grand total
within her pivot table. I'm having problems with this as when I add a column
and put in a formula it changes the data in the whole pivot table. Can I add
a column and get the average of the grand total without changing the data in
the pivot table itself? Appreciate any suggestions!!

 

[Guest]

Here is how the data is set up:

Pay type OT
Sum of FTE Act Fiscal Period
Center Jan Feb Mar Apr May Jun Jul
Grand Total
11513013 3.12 3.36 3.43 2.85 1.68 1.69 1.54 17.67
11513014 - 0.02 0.13 0.02 0.07 0.11 0.10
0.45
11513017 0.67 2.00 1.25 0.68 0.53 0.87 1.24
7.24