请教高手，关于Workbooks.add函数

//Microsoft.Office.Interop.Word.Application wordApp = new Microsoft.Office.Interop.Word.Application();
            //object filename = @"D:\tools\tbs\tbs\TMD\TMDBLL\EmailDot\Post Heads Up Report.dot";
            //wordApp.Visible = false;
            //Microsoft.Office.Interop.Word.Document doc = null;
            //doc = wordApp.Documents.Add(ref filename, ref a, ref c, ref b);