private void ShowHelpDialog()
 {
     if (m_helpDialog == null)
     {
         m_helpDialog = new HelpDialog();
         m_helpDialog.Closed += new EventHandler(this.helpDialog_Closed);
         m_helpDialog.Show();
     }
 }
 private void helpDialog_Closed(object sender, EventArgs e)
 {
     m_helpDialog = null;
 }