Help, Please, with DAX Date Processing

I’m honing my DAX skills in Power BI Desktop, and I’ve run into a snag that I hope the community can help me with.

I’ve been using Reza Rad’s excellent book, Power BI from Rookie to Rock Star: Book04 – “Power BI Modeling and DAX”.  In this exercise, we use the MS Adventure Works DB to determine the Total Sales to each customer and, using a slicer to select the most-recent “x” number of days, we then calculate the total sales dollars for each of those customers for that selected period.

I had no problem with getting the Total Sales per customer but, trying to get the Sales per Customer for the selected time period, PBI runs for 20+ minutes, then gives an error of “not enough memory” on my 8 GB PC, with essentially nothing else running.  As these tables are used for training, they are fairly small, so I'm sure I'm doing something wrong.

In the book the code to select the Sales for the selected time period is as follows:

Last Period Revenue = CALCULATE(

SUM(FactInternetSales[SalesAmount]),

DATESBETWEEN(

DimDate[FullDateAlternateKey],

DATEADD(LASTDATE(DimDate[FullDateAlternateKey]),-1*[Selected Period],DAY),

LASTDATE(DimDate[FullDateAlternateKey])

)

)

After the first failure, I copied the essential columns of the Adventure Works FactInternetSales table to a new table, using “SELECTCOLUMNS” but this didn’t work either.  (I do still have the original table in PBI, but I believe that shouldn’t impact the extract, as we’re now only working with the subset.)

I then tried simplifying the code, creating the following measures (Selected Period is the slicer's number of days for creating the range):

First Date In Range = (CALCULATE([Last Date In Range] -[Selected Period]))

Last Date In Range = LASTDATE('Subset of FactInternetSales21'[OrderDate])

With Selected Period = 60, I used cards to verify these two values: 6/1/2008 and 7/31/2008 are correct.

I tried another approach for the results columns, calculating it as:

Last Period Revenue = CALCULATE(SUM('Subset of FactInternetSales21'[SalesAmount]), DATESBETWEEN(DimDate5[FullDateAlternateKey], [First Date In Range], [Last Date In Range]))

This still locks up PBI.

Any suggestions would be most appreciated!!