Answer

Option 1: Use Nested Level of Detail (LOD) Expressions

1. Drag Regions to Rows. 
2. Drag Measure Names to Columns and Measure Values to Text. 
3. Select Analysis > Create calculated field
4. Name the calculated field "Maximum regional sales (LOD)", enter the following formula and click OK: 

   {FIXED : MAX( { FIXED [Regions] : SUM( [Sales] ) } ) }

5. Add the calculated field to the Rows shelf
   1. Right click the calculated field on Rows and convert it as Discrete
   2. Right click the calculated field on Rows and select Format... to remove or customize decimals. 
6. Select Analysis > Create calculated field
7. Name the calculated field "Region with highest sales Filter (LOD)"
8. Enter the following formula and click OK: 

   { FIXED [Regions] : SUM([Sales]) } = [Maximum regional sales (LOD)]

9. Add the calculated field to the Rows shelf
10. Select Analysis > Create calculated field
11. Name the calculated field "Region with highest sales (LOD)", enter the following formula and click OK: 

    IF { FIXED [Regions] : SUM( [Sales] ) } = [Maximum regional sales (LOD)]
    THEN [Regions]
    END
    

12. Drag [Region with highest sales (LOD)] to the Rows shelf.

Option 2: Use table calculations

1. Drag Regions to Rows. 
2. Drag Measure Names to Columns and Measure Values to Text. 
3. Select Analysis > Create calculated field
4. Name the calculated field "Maximum Sales (table calc)", enter the following formula and click OK: 

   WINDOW_MAX( SUM( [Sales] ) )

5. Add the calculated field to the Rows shelf
   1. Right click the calculated field on Rows and convert it as Discrete
   2. Right click the calculated field on Rows and select Format... to remove or customize decimals. 
6. Select Analysis > Create calculated field
7. Name the calculated field "Region with highest sales (table calc)", enter the following formula and click OK: 

   IF SUM( [Sales] ) = [Maximum Sales (table calc)]
   THEN MIN( [Regions] )
   END
   

8. Drag [Region with highest sales (table calc)] to the Rows shelf.

Additional Information

• Table calculations require that all dimensions needed to compute the calculations always be included in the view. In this case, since we want to find the region with the highest sales, [Regions] must be in the view.