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How can I have a kind warning if I am adding a text to the cell which was already added somewhere in previous cells of the same column?

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Did you had the time to evaluate my solution? –  Jacob Jan Tuinstra Apr 28 '13 at 19:19

1 Answer 1

I've prepared an example file for you: Avoiding Duplicates. The only formula used, is the following:


Added example for None Case Sensitive entries:

With Google Apps Script, you can really make it more visual. With the following script, that uses the onEdit trigger function, you can make the font color turn red:

function onEdit() {
  var sh = SpreadsheetApp.getActiveSpreadsheet().getActiveSheet();
  var status = sh.getRange("C1").getValues();
  var cell = sh.getActiveCell();

  if(status == "Invalid") {
  } else {

If you set conditional formatting in A1 on Invalid to be marked red, then a visual change will make you realize that a duplicate value has been entered, see pic:
enter image description here


  1. you need to fix the headers, in order to keep seeing visual change.
  2. you need to pay attention, because all of this isn't bullet proof !!
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Nice solution. I really enjoyed it. –  Saeed Neamati Sep 21 '13 at 14:49

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