Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)
    Dim arr As Variant
    arr = Intersect(Columns("M:N"), ActiveSheet.UsedRange)
    Dim yy As Long
    For yy = 2 To UBound(arr, 1)
        If arr(yy, 1) = "Иное(обязательный комментарий)" Then
            If arr(yy, 2) = "" Then
                MsgBox "Не заполнены ячейки в столбце M.", vbExclamation, "M:N"
                Cancel = True
                Exit For
            End If
        End If
    Next
End Sub