Filter Top 15 customers in pivot table ?

[#1]

Dear Friends ;

I designed finance related reports with multiple expressions like total outstanding , billing , collection ...etc using pivot chart .

But i want to filter top 15 customer based on Billing or total outstanding . if user select parameter as O/S , i want to show top 15 customer based on O/S , it user select billing , i want to show top 15 customer based on Billing .

Pls suggest how to achieve this in pivot chart . 

[Gysbert_Wassenaar]

See this document: Show Top Performers

Or this one: Display Top n by Dimension in Pivot table