O7 Duplicate values in a list using search

[Martin Obongita]

Hi All,
This is an Omnis 7 question.
I have the procedure below to search for duplicate records in a list (I found this method in another thread):
---Set current list #L1    
Clear sort fields    

Set sort field E1_CODE    
Sort list    
Set search as calculation {(#L1.[#L+1].[E1_CODE]=#L1.E1_CODE)|(#L1.[#L-1].[E1_CODE]=#L1.E1_CODE)}    
Search list (From start,Select matches (OR),Deselect non-matches (AND))    
Go to next selected line (From start)    ---
It does not seem to search the list as expected, for me.
This has led me to look for help here. How do I search for duplicate rows in a list in Omnis 7?
RegardsMartin.