About Bho call OnNewWindow3 method

Here is my code,when i use [window.open] in my page, this method is not fired,is there any one can tell me why,thanks very much!

webBrowser = site != null ? (SHDocVw.WebBrowser)site : null; webBrowser.NewWindow3 += new DWebBrowserEvents2_NewWindow3EventHandler(this.OnNewWindow3); private void OnNewWindow3(ref object ppDisp, ref bool Cancel, int dwFlags, string bstrUrlContext, string bstrUrl) { MessageBox.Show("OnNewWindow3"); }