protected override void OnStartUp()
{
   //...
   foreach (NinjaTrader.Cbi.Account a in NinjaTrader.Cbi.Globals.Accounts)
   {
      a.OrderStatus += new OrderStatusEventHandler(OnOrderUpdate); // subscribe handler for all accounts

      // subscribe another useful event handlers
      // a.Execution += new ExecutionUpdateEventHandler(OnExecution);
      // a.PositionUpdate += new PositionUpdateEventHandler(OnPositionUpdate);
      // a.Connection.ConnectionStatus += new ConnectionStatusEventHandler(OnConnectionStatus);
      // a.AccountUpdate += new AccountUpdateEventHandler(OnAccountUpdate);
   }
   //...
}

protected override void OnTermination()
{
   //...
   foreach (NinjaTrader.Cbi.Account a in NinjaTrader.Cbi.Globals.Accounts)
   {
      a.OrderStatus -= OnOrderUpdate;	// unsubscribe handler

      // unsubscribe another useful event handlers
      // a.Execution -= OnExecution;
      // a.PositionUpdate -= OnPositionUpdate;
      // a.Connection.ConnectionStatus -= OnConnectionStatus;
      // a.AccountUpdate -= OnAccountUpdate;

   }
   //...
}

// handle event
private void OnOrderUpdate(object sender, OrderStatusEventArgs e)
{
   if (e.Order.Account == acc && e.Order.Instrument == Instrument)  // order status changed for order on my account and instrument only
   {
      // do something useful
      Print(e.Order.ToString());	
      Print("Order state = " + e.Order.OrderState);
      Print("Order action = " + e.Order.OrderAction)
      if (e.Order.OverFill)	
      {
         // handle overfill
      }		
      // etc
   }
}

// private void OnExecution(object sender, ExecutionUpdateEventArgs e)
// {
//     ...
// }

// private void OnPositionUpdate(object sender, PositionUpdateEventArgs e)
// {
//     ...
// }

// private void OnConnectionStatus(object sender, ConnectionStatusEventArgs e)
// {
//     ...
// }

// private void OnAccountUpdate(object sender, AccountUpdateEventArgs e)
// {
//     ...
// }