Bookmarks problems - automating Microsoft Word with C#

private void button1_Click(object sender, EventArgs e)
        {
            object oMissing = System.Reflection.Missing.Value;
            object oEndOfDoc = "\\endofdoc"; /* \endofdoc is a predefined bookmark */

            //Start Word and create a new document.
            Word._Application oWord; //Define
            Word._Document oDoc; //Define
            oWord = new Word.Application();//start Word
            oWord.Visible = true;//show Word

            Object oTemplatePath = "C:\\social_assesment_templ.doc";//find the document
            oDoc = oWord.Documents.Add(ref oTemplatePath, ref oMissing, ref oMissing, ref oMissing); //load social_assesment_templ.doc into the document
            Object oBookMark = "Applicant_name"; //A bookmark in the doc file.
            oDoc.Bookmarks.Item(ref oBookMark).Range.Text = "John Doe";//change 'oBookMark''s text range to "John Doe"
            Object fileName = "C:\\TestFile.doc";//Set new file name
            oDoc.SaveAs(ref fileName,ref oMissing, ref oMissing,ref oMissing, ref oMissing,ref oMissing, ref oMissing,ref oMissing, ref oMissing,ref oMissing, ref oMissing, ref oMissing,ref oMissing, ref oMissing,ref oMissing, ref oMissing);//save as 'filename'
        }

oDoc.Bookmarks.Item(ref oBookMark).Range.Text = "John Doe";//change 'oBookMark''s text range to "John Doe"//The 'Item' is underlined: ...Word.Bookmarks does not contain a definition of 'Item'. However, I found this on one of microsoft's sites.