Modular Result in a Pivot Table - Calculate the Result when i 've reached up 85% of a odd variable - Fractile

[perry7]

Hi!
 I've made an histogram where I see:
- Numbers of Packages
- Time (Lead Time from Arrived to Shipping)

I need to study the Lead Time when i 've reached up 85% of numer packages ordered by Lead Time Ascendend 
(see picture under)
  

I've to put this result on Pivot Table, where i have categories variables as Area, Store, Region, Package Type, Good Type...

The formula of my goal is:
=Max({< [LeadTime]={"<= $(=fractile([Lead Time],0.85))"} >} [Lead Time])

But if I put it in a Pivot, I ve :

The result is not modular when i change  the categories variables, but its always the same!
What shall I write ??

Hoping a solution,
marco