Question : Dlookup to prevent duplicate entries

I have the following code in place to check for duplicate entry in [Certificate Number].  Each time I test it with duplicate date I get an error message telling me I
cancelled the previous operation.  I'm sure I've messed up the syntax for the dLookup function.  Can anyone help?

Thanks!

Rose Marie

---------------------------Begin code--------------------

Private Sub Contract_Number_BeforeUpdate(Cancel As Integer)

If DLookup("[Certificate Number]", "tblAFRateMovement", "[Certificate Number] = '" & Me.txtContractNumber & "'") Then

Me.Undo

 MsgBox "Warning! Certificate Number " _
        & txtContractNumber & " has already been entered." _
        & vbCr & vbCr & "Please try again.", vbExclamation, "Duplicate Certificate Number!"

End If

End Sub
-------------------------End code----------------------------------------

Answer : Dlookup to prevent duplicate entries

PAQed with points refunded (125)

Computer101
EE Admin