Hello. I'm using Excel 2010.

I'm not much of a spreadsheet designer, so I'm hoping what I want to do is fairly simple.

I want to flag duplicate dates somehow. Here's what I mean:

My spreadsheet has columns for Last Name, First Name, etc. The standard data. One column in particular has dates, formatted like this: 11/14/12.

All I want is for Excel to display a warning or a flag of some sort, if I type in a date that is already in that column. It is not necessary for Excel to inform me which cell has the already-entered date.

So…let's say 03/18/10 is in cell D-10.

If I enter 03/18/10 in oh, let's say cell D-59, I want Excel to inform me somehow that this date has already been entered elsewhere in the same column.

Is this possible? If so, then what is the easiest and most practical way to accomplish this?

If you require further details from me, please let me know.

Thank you very much. J. Danniel

One way would be using Conditional formatting
If you plan to always enter your reference date in D59 try the following :
Select the range containing tour dates to check (say D150) - go to Conditional Formatting - Use a formula
As formula enter and choose the format you want when the condition is true The formatting of the duplicate will then change in your range

If the dates in range D150 are not true dates, let us know so w can help further

There are also other possibilities

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Hi tatihulot

I am not a great lover of the built in Conditional Formatting. But here you go, nice and simple. Select the range you wish to conditionally format. Home tab > Styles > Conditional formatting > Highlight cell rules > Duplicate values > Format as required.

@Kevin
As the OP explained, he wants to enter a date in a cell and check a range to see if that date is already there.
I'm afraid the solution you proposed will not help in this case

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@ Pecoflyer

If I were you I should read the question again.

The OP has written "I want to flag duplicate dates somehow" & "If I enter 03/18/10 in oh, let's say cell D-59". Has he said that he wants to reference D59 all the time!! I think not.

Rightly or wrongly, the OP has requested that there is some kind of warning that if he enters a date in column D that already exist then flag them. so what you are suggesting, is the answer I come up with will not work. Is that correct!!

I agree it can also be interpreted that way

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