Calcul sur VBA

Private Sub CommandButton1_Click()
Dim c1 As Range
Dim c2 As Range

  ActiveCell.Activate
  With Application.Selection
    On Error GoTo Gestion_Erreur
    If .Count = 2 Then
      If Split(.Address, "$")(1) = Split(.Address, "$")(3) Then
        'Si 2 cellules de la même colonne ...
        Set c1 = Range(Split(Replace(.Address, ":", ","), ",")(0))
        Set c2 = Range(Split(Replace(.Address, ":", ","), ",")(1))
        c2.Offset(0, 1).Value = c2.Value - c1.Value   'ou l'inverse
      Else
        Err.Raise vbObjectError + 513
      End If
    Else
      Err.Raise vbObjectError + 514
    End If
    On Error GoTo 0
  End With
Exit Sub

Gestion_Erreur:
  
  Select Case Err.Number
    Case 13
      MsgBox "Erreur : Valeur(s) non numérique(s)", vbExclamation
    Case vbObjectError + 513
      MsgBox "Les 2 cellules doivent être dans la même colonne", _
             vbExclamation
    Case vbObjectError + 514
      MsgBox "Sélectionner 2 cellules dans la même colonne", _
             vbInformation
    Case Else
      MsgBox "Erreur " & Err.Number & " - " & Err.Description, _
             vbCritical
  End Select
End Sub