How to make a field created a part of the Pivot Table Field List?
 

I have my Pivot table, and created a (sum of employees) which gives me the
sum of
all employees grouped by department. Now i would like to add this field to
the pivot table field list so i can manipulate that field in a calculated
field. I hope you can help me out, or tell me where can i learn about this
subject. thank you,,,,,