How to add a caculated field to sum an entire column in pivot table?

[tonywatsonhelp]

Hi Everyone,
I have a pivot table and one column is called "Average of price"

Next to it I'd like to add a calculated field that just sums the column up so just Sum("Average of price")
but i cant get it to work,
can someone please give me the formula i need to do this.
if my data is not enough n example will do i just need to be pointed in the right direction.



thanks

Tony