to calculate rolling 12 months sales (rolling from the max date within a selected time range). For example, if I select 09/20/2018-09/24/2018, I want the expression sum up sales from 09/24/2017-09/24/2018.
However, in current expression, if I select 09/20/2018-09/24/2018, it will show me sales for 09/20/2018-09/24/2018. I don't know how I can fix this expression... Please help!!