using a "sum of ..." field in a calculated field

Hi, let's see if you can help me with this question:
I have a sheet with some fields, one of them is 'nș of ind'. I then create a pivot table and add a data field with 'nș of ind' as an average xlaverage (Function = xlAverage), that field is called "ind avrg", for example. Now I need to add a calculated field who uses that value (the average of nș of ind) in a function, something like "ind avrg" * 3 but of course in the list of fields available for my new calculated field doesn't appear my field "ind avrg", only the data field "nș of ind". I've tried using = average("nș of ind")* 3 in the calculated field but I get wrong data.
Don't know if I'm explaining it well.

I need to use a field of the pivot table (not from the data sheet) as a source for a calculated data. If you can provide a solution... even a vba solution would be welcomed.

Thank you very much.