Private Sub Worksheet_SelectionChange(ByVal Target As Range)
If Target.Count > 1 Then Exit Sub
If Target.Address = "$B$1" Then
Range("A1").Value = 1
ElseIf Target.Address = "$C$1" Then Range("A1").Value = 2
ElseIf Target.Address = "$D$1" Then Range("A1").Value = 3
End If
End Sub