Avg RangeAvg

[Anonymous]

I have a measure that I am trying to create.  It will be used in table to show average of total sales for the day for the previous 30 days (rolling).  So far I have the following expression:

Avg({<Date = {">=$(=Date(Max([completed_date.autoCalendar.Date]))-30)))"}>}Sales)

The issue with this formula though is that it calculates the average of order totals over the last 30 days, not total sales for day average.  Any edit to this expression that will get me closer to correct average I am searching for?  Attached table where I would like to use measure.