.NET 4.x Как загружать файл из программы, не меняя код? - C#

Word.Application app = new Word.Application();
//---------------------------------------------------------------------------------------------------------------------
            Object fileName = @"C:\Users\JPro.JPro-ПК\Desktop\WordToXpsDocument\4 глава.docx";
// --------------------------------------------------------------------------------------------------------------------
            Object missing = Type.Missing;
            app.Documents.Open(ref fileName);
            Word.Find find = app.Selection.Find;

            string[] array = new string[2];
            string[] array1 = new string[2];
            array[0] = textBox1.Text;
            array1[0] = textBox2.Text;
 
            for (int i = 0; i < array.Length; i++)
            {
                find.Text = array[i];
                find.Replacement.Text = array1[i];
                Object wrap = Word.WdFindWrap.wdFindContinue;
                Object replace = Word.WdReplace.wdReplaceAll;
                find.Execute(FindText: Type.Missing,
               MatchCase: false,
               MatchWholeWord: false,
               MatchWildcards: false,
               MatchSoundsLike: missing,
               MatchAllWordForms: false,
               Forward: true,
               Wrap: wrap,
               Format: false,
               ReplaceWith: missing, Replace: replace);

            }
            app.ActiveDocument.Save();
            app.ActiveDocument.Close();
            app.Quit();

  Object fileName = @"C:\Users\JPro.JPro-ПК\Desktop\WordToXpsDocument\4 глава.docx";