In most cases yes, if its an order placed after hours you can place another order with the option during checkout - add to previous order and put the previous order number in the comment section. 

If its during normal business hours I would suggest calling or sending us a message after the order is placed so we can make arrangements to add it to your order.

In both instances there is no guarantee we can fit it in the same box but we will always do what we can to minimize any additional shipping cost