@upwardD ,
The problem here is your data model. Whenever you are doing time intelligence calculations/analyses, your data model needs to include a proper date table that is marked as such. I very strongly recommend using @Melissa’s awesome Extended Date Table for this purpose. That date table includes a field entitled WeekEnding.
All you would need to do is add a calculated column to that table:
WeekStarting = Dates[WeekEnding] - 6
That should solve your problem here, plus give you an array of other extremely powerful capabilities for additional time intelligence analyses.
I hope this is helpful.
- Brian