Prevent data duplication with condition - vba

Question

I want to setup a data duplication check on a text box which is used to input serial numbers.
If the entered serial number is already found in the database, it should call a MsgBox to alert the user before clearing the value in the text box.
However, if the entered serial number contains "RW", the check should be disabled.
Private Sub Serial_Number_AfterUpdate()
Dim NewSerialNumber As String
Dim stLinkCriteria As String
NewSerialNumber = Me.Serial_Number.Value
stLinkCriteria = "[Serial_Number] = " & "'" & NewSerialNumber & "'"
If Me.Serial_Number = DLookup("[Serial_Number]", "Esagon_End", stLinkCriteria) Then
MsgBox "This serial number, " & NewSerialNumber & ", has already been entered into the database." _
& vbCr & vbCr & "Please check the serial number again.", vbI, "Duplicate information"
Me.Undo
End If
End Sub
If this cannot be done with VBA I'm open to other methods like queries. Thank you.

Answer 1

Looking at what you have asked, I think this is what you are looking for. If it isn't then leave a comment and I'll try to update my answer.
Private Sub Serial_Number_AfterUpdate()
'If it doesn't contain "RW"
If InStr(Me.Serial_Number, "RW") = 0 Then
'If serial number not in the database
If DCount("*", "Esagon_End", "Serial_Number = '" & Me.Serial_Number & "'") > 0 Then
'Alert user and blank the text box
Call MsgBox("The serial number " & Me.Serial_Number & " is already in the database." _
& vbCrLf & vbCrLf & "Please check the serial number you are entering.", _
vbInformation, "Duplicate Serial")
Me.Serial_Number = ""
End If
End If
End Sub