Saturday, September 1, 2012

yogi_Check For Duplicates In Columns A And B And Post in Column C Row by Row

Yogi Anand, D.Eng, P.E.       Google Spreadsheet    Post  #723   Sep 01, 2012     www.energyefficientbuild.com.

user jay Curtis said: (https://productforums.google.com/forum/#!category-topic/docs/jF53BFoXkFg)
VLOOKUP to check for same value within column??
This seems like the most valuable use of the VLOOKUP function, yet I can't find a straight answer on how best to implement it. Apologies if this is a regular question, i scanned this section of the forum looking for similar topics..

example:

      Column A:     Column B:
      Date values   Numerical Values (unique URL IDs in numerical form)

1    1/9/12            18340
2    29/8/12          19560
3    27/8/12          17350 

I am looking for a single formula that will scan the whole column within the sheet and alert me if there is more than one entry of the same value just within the column i am entering data into

ie:

      Column A:     Column B:
      Date values   Numerical Values (unique URL IDs in numerical form)

1    1/9/12            18340
2    1/9/12            19560
3    27/8/12          18340 

or perhaps: 

      Column A:     Column B:      Column C: (Check value column)           
      Date values   Numerical Values (unique URL IDs in numerical form)

1    1/9/12            18340            A2 : DBL! 
2    1/9/12            19560            B3:  DBL!
3    27/8/12          18340 

      Column A:     Column B:      Column C: (Check value column)
      Date values   Numerical Values (unique URL IDs in numerical form)

1    1/9/12             18340            NO DBL 
2    29/8/12           19560            NO DBL
3    27/8/12           17350 

This seems very simple, just can't work out how to get it to blanket scan for double entries!
Many thanks,
JC 
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following is a solution to the problem