Creating a unique field in Access

I am building a database in ACCESS and have created a field called "Computer ID".  I want this field to be unique.  How do I set it up so that duplicate entries cannot be added?
Will Schmidtowner Asked:
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you could set it in field settings, you should set this field as indexed and require "duplicates are not allowed"
Scott McDaniel (Microsoft Access MVP - EE MVE )Infotrakker SoftwareCommented:
If you want Access to automatically assign the value, set it to Autonumber, and then set the duplicate setting as above.

You can also set it as the Primary Key of the table, which will set it to be unique as well.
Will Schmidtowner Author Commented:
OK, that works OK except I would like to customize it in the form. on the "error now" pic is what comes up when I try to enter a name that is already there. the second pic is what I would like it to look like.
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You could add your custom error message with a sub like the following:

Private Sub Form_Error (DataErr As Integer, Response As Integer)
     MsgBox "Entry already on file"
     Response = acDataErrContinue
  End If
End Sub

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Will Schmidtowner Author Commented:
Thanks for helping me with this issue.  The problem has been resolved.
Scott McDaniel (Microsoft Access MVP - EE MVE )Infotrakker SoftwareCommented:
Are you sure you intended to accept only that comment as your solution? The first two comments should have given you an answer to your question, and the last would have been an answer to your followup question.
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