code to enter my message not working

Hi
Thanks for all the advice i thought this would do the trick but even if i dont type in a duplicate number I get the message
You have entered a duplicate npan number. Please check your records",

can anyone help im so close " I think"



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Private Sub npan_elec_AfterUpdate()
On Error GoTo Err_npan_elec

DoCmd.RunCommand acCmdSaveRecord

Err_npan_elec:
If Err.Number = "3022" Then
MsgBox "You have entered a duplicate npan number. Please check your
records", vbOKOnly
Me.inv_no_elec.SetFocus
Me.npan_elec = Null
Me.npan_elec.SetFocus
Else: MsgBox "An unforseen error has occured please contact your
admisistrator", vbOKOnly
Me.inv_no_elec.SetFocus
Me.npan_elec = Null
Me.npan_elec.SetFocus
End If

End Sub