how newdocument event is fired through shared add-in for MSoffice word?

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C#2.0

C#

I created one shared add-in in visual studio 2005. In this i fired three event for ms word
1)NewDocument(is fired when we open new word document)
2)DocumentOpen(is fired when already created word document is opened)
3)DocumentBeforeClose(is fired when document is closed (any new or already created))
but in my case NewDocument event is not working i don't knw why the last two event is working fine and the DocumentBeforeClose event is worked for new document also.
my code for new document is:-

public void OnStartupComplete(ref System.Array custom)
{
wb = (Word.Application)System.Runtime.InteropServices.Marshal.GetActiveObject("Word.Application");
if (wb.Documents.Count > 0)
{
object docIndex = 1;

MessageBox.Show(wb.Documents.Count.ToString() + "\r" + wb.Documents.get_Item(ref docIndex).Name);
}
((Word.ApplicationEvents4_Event)wb).NewDocument += new Word.ApplicationEvents4_NewDocumentEventHandler(Application_NewDocument);
}

void Application_NewDocument(Word.Document Doc)
{
MessageBox.Show("New: " + wb.ActiveDocument.Name);
openingTime = DateTime.Now.ToLocalTime();
}


why this event is not fired when i open new word document or can say on open MSword.