Median; how to?

[ali_hijazi]

Dear

I got a pivot table (check attached) with one expression:

(sum
       (
              {
                     <
                           Flag = {'Sales'}
                           ,[Payroll Month]=
                           ,[Payroll Year]=
                          
                     >
              }
              if(
                     (isnull(DeactivationDate) or DeactivationDate > PeriodDate)
                      and PeriodDate >= num(addMonths(Date($(vForeCastDate)),-11)) and PeriodDate<=num(DayStart(MonthEnd(date($(vForeCastDate))))) ,AmountInUSD,0
                 )
    )
  )
  /[Selling Area]

this expression is giving correct results

now I want to calculate the Median of the values displayed in another column

As per the attached excel sheet the Median is the value 9,327

I used Median(above_expression) but got nulls as per attached image

Please advise