replace textbox in word documents in c#

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C#3.0

C#

hi i have a word 2007 document , my word document have 4 text box control, i want to replace these text boxes with input strings in My apllication in c#,attention this ,i do not want to replace text type in word, i want to replace text box control of word document;

FindAndReplace(varWord, @"#Sabbat_School#", Properties.Settings.Default.SchoolName);

 private void FindAndReplace(Word.Application wordApp,
                   object findText, object replaceText)
       {
           object matchCase = true;
           object matchWholeWord = true;
           object matchWildCards = false;
           object matchSoundsLike = false;
           object matchAllWordForms = false;
           object forward = true;
           object format = true;
           object matchKashida = true;
           object matchDiacritics = true;
           object matchAlefHamza = true;
           object matchControl = true;
           object read_only = false;
           object visible = true;
           object replace = 2;
           object wrap = 1;
           
           wordApp.Selection.Find.Execute(ref findText, ref matchCase,
               ref matchWholeWord, ref matchWildCards, ref matchSoundsLike,
               ref matchAllWordForms, ref forward, ref wrap, ref format,
               ref replaceText, ref replace, ref matchKashida,
               ref matchDiacritics,
               ref matchAlefHamza, ref matchControl);
       }

this code is replace #Sabbat_School# to Properties.Settings.Default.SchoolName in word documents , but it replace text and does not work in text box control in word,
i want a code that work in text box control in word. please help me