I've found the solution but not so easy.
Before chm help  , or earlier version of MSDN Library , Microsoft was working
for supplying a good help document. At least for main methods , like Find method
, there was a sample.
I am using c# 2005 , VSTO2005 and related MSDN Library. There is no any sensible
explanation or sample.

   public partial class ThisDocument
   {
       Microsoft.Office.Interop.Word.Selection activeSelection = null;
       Microsoft.Office.Interop.Word.Range range = null;
       private void ThisDocument_Startup(object sender, System.EventArgs e)
       {
           this.SelectionChange += new
Microsoft.Office.Tools.Word.SelectionEventHandler(ThisDocument_SelectionChange);

           for (int i = 1; i < this.Paragraphs.Count+1; i++)
           {
               range = this.Paragraphs[i].Range;
               range.Select();
               string word = "";
               string response = "";
               bool ret = parseWordAndResponse(ref word, ref response);
               ret = insertWordToDatabase(word, response);
           }

       private void ThisDocument_SelectionChange(object sender,
Microsoft.Office.Tools.Word.SelectionEventArgs e)
       {
           activeSelection = e.Selection;
       }

C#
public interface Find

Word Primary Interop Assembly Reference  
Find.Execute Method  

Runs the specified find operation.
Namespace: Microsoft.Office.Interop.Word
Assembly: Microsoft.Office.Interop.Word (in microsoft.office.interop.word.dll)

bool Execute(
    [In, Optional] ref object FindText,
    [In, Optional] ref object MatchCase,
    [In, Optional] ref object MatchWholeWord,
    [In, Optional] ref object MatchWildcards,
    [In, Optional] ref object MatchSoundsLike,
    [In, Optional] ref object MatchAllWordForms,
    [In, Optional] ref object Forward,
    [In, Optional] ref object Wrap,
    [In, Optional] ref object Format,
    [In, Optional] ref object ReplaceWith,
    [In, Optional] ref object Replace,
    [In, Optional] ref object MatchKashida,
    [In, Optional] ref object MatchDiacritics,
    [In, Optional] ref object MatchAlefHamza,
    [In, Optional] ref object MatchControl
);