I couldn't suppress your nulls yet but i simplified your formula:
IF [N Periods Back ] <= 3 and
[Date] >= dateadd([Comparison Period],-[N Periods Back ],[Start Date]) and [Date]<= dateadd([Comparison Period],-([N Periods Back ]-([N Periods Back ] - 1)),[End Date]) then [Channel costs]
Luciano Vasconcelos Thanks lot for simplifying the formula !
There is still a problem that , the values should be displayed for the same date range for months ( N periods back ) i.e... if i select 01/08/16 - 09/08/16 and n periods back 2 then i should have the previous period values for 01/07/16- 09/07/16 and 01/06/16 -09/06/16.
At the moment the correct values are displayed only if n period back = 1 and for the rest of values it gives back the total month values. Couldn't figure out whats going wrong here
Could you please help me out with this ?