Please attach a mock up workbook.
Hi Its a little difficult without a workbook as Deepak noted
but have you tried a lookup function on the calculation you used to determine the median
it you would be of the form % growth = ( (lookup(median formula),-1) -( Medain formula for the period))/(lookup(median formula),-1)
You may have to drop in the actual for the median formula -
- WINDOW_MEDIAN(COUNT(Sale ID))
Let me know if that helped