Public Sub AddButton()
    Dim wb As Workbook
    Dim ws As Worksheet
    Dim btn As OLEObject
    Dim cm As CodeModule
    Dim lngFirstLine As Long
    
    Set wb = ThisWorkbook
    Set ws = ActiveSheet
    Set btn = ws.OLEObjects.Add( _
      ClassType:="Forms.CommandButton.1", _
      Link:=False, _
      DisplayAsIcon:=False, _
      Left:= 536 . 25 , _
      Top:= 458 . 25 , _
      Width:= 72 , _
      Height:= 24 )
    
    btn.Object.Caption = "Назад"
    
    Set cm = wb.VBProject.VBComponents(ws.CodeName).CodeModule

    With cm
        lngFirstLine = .CreateEventProc("Click", btn.Name) +  1 
        .InsertLines lngFirstLine, _
          "    Msgbox ""Say Hello!"",vbOkOnly"
    End With
    
    Set cm = Nothing
    Set ws = Nothing
    Set wb = Nothing
End Sub