Writing formulas using the calculated field of a pivot table

[mexaria]

All,

I got an easy one for you Excel geniuses..

It concerns the calculated fields in a pivot table (PT). I want to add a field in a PT that is calculated using standard deviation and average of existing fields in the datasource. But how I declare standard deviation and average in the "Formula" box within the "Insert Calculation Field" window? There is no automatic search of functions as it exists when writing formulas in regular excel cells..

Thank you!!