Find duplicate row values while comparing two columns

Hello, 

I am new here and new to BI.

I have a table with postcodes and locations, e.g. 

AL10 0AB Hatfield

AL10 0AB Hatfield

DN4 0QN Doncaster

DN4 0QN Sheffield

DN4 0QN Leeds

where postcode is in one column and a location is in another. 

I want to create a new column which will tell me where I have duplicate (repeating) postcodes that are allocatied to a different location. In above list, AL10 0AB would return a NO or FALSE becuase it's a duplicate at the same location. However, DN4 0QN would return YES or TRUE. 

Many thanks for your help in advance. 

Nena