SAMPLE DATA IS GIVEN BELOW:
WRITE THE NAME YOU WANT TO CHECK FOR DUPLICATE ENTRY IN CELL C4 AS SHOWN BELOW:
WRITE THE FORMULA IN CELL D7 & COPY IT FOR CELL ADDRESS AS SHOWN BELOW:
WRITE THE FORMULA OF VLOOKUP IN CELL D4 AS SHOWN BELOW:
IF THE NAME IS THERE IN THE LIST YOU WILL GET THE CELL ADDRESS AS RESULT AS SHOWN BELOW:
For more details on vlookup check my video on /video/excel-basics-vlookup-2450.asp
For excel file on this example with macros check share file section: IDENTIFY DUPLICATE ENTRY.
Note: Hypothetical data has been used in the example.