SUMMARIZECOLUMNS - Only the top value for multiple groupings

[-Rem-]

I have a table that contains information about regions and sellers active in these regions. Related to this table is also a table of sales. With SUMMARIZECOLUMNS I now want to create a table that returns the top salesperson by units for each region. What I have tried so far is this:

Top Sellers= SUMMARIZECOLUMNS('Customers'[Region],'Customers'[Salesperson],"Unit Sales",[Sum of UnitQTY])

This produces a table such as:

Region	Seller	Unit Sales
A	Adam	5000
A	Eve	200
B	Steve	4000
B	Eve	8000
C	Adam	5
C	Steve	100
C	Eve	50

However my desired result would be this: 

Region	Seller	Unit Sales
A	Adam	5000
B	Eve	8000
C	Steve	100

How can I achieve this using SUMMARIZECOLUMNS or an aquivalent function that will produce a new table?

[amitchandak · Accepted solution]

@-Rem- , In place of unit Sales in summarize column, use the following columns

Top 1 Rank = CALCULATE([Sales],TOPN(1,all(Customers[Region]),[Sales],DESC),VALUES(Customers[Region]))