Gary is suggesting not using a macro, but using code like this
Private Sub Worksheet_Change(ByVal Target As Range)
Const WS_RANGE As String = "A1,B1"
On Error GoTo ws_exit:
Application.EnableEvents = False
If Not Intersect(Target, Me.Range(WS_RANGE)) Is Nothing Then
With Target
Me.Cells(.Row, "C").Value = Me.Cells(.Row, "A") + _
Me.Cells(.Row, "B").Value
End With
End If
ws_exit:
Application.EnableEvents = True
End Sub
'This is worksheet event code, which means that it needs to be
'placed in the appropriate worksheet code module, not a standard
'code module. To do this, right-click on the sheet tab, select
'the View Code option from the menu, and paste the code in.
--
HTH
RP
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