Median Absolute Variance Power Pivot table

[BoVas]

Hello,

I'm creating a dashboard that keeps track of the Coefficient of dispersion. For this, I created a column that calculates the absolute variance from the median. I'm using a Medianx(sales,[ratio]) however this calculates the ABS Variance using the median of all the data. I would like for excel to use whatever median is being filter through the pivot.

Thank you in advance for your help!