How do I change the default setting for 'Notify Customer' to 'off' when I add comments or change order status on admin/orders.php?

I want to be able to change status as the order handling progresses without sending an email to the customer for every step. (I have status like "hold for payment", "waiting for payment to clear", "payment cleared", "packing", etc.) The customer can see all this if he/she wants by logging in and viewing, however I expect normally to send emails for "back ordered" and "shipped". In those cases I will manually check the box to notify the customer.