Repositioning an Order in F2

[Formaldehyde]

If I give an order that I wish to cancel or reposition in the F2 screen, how do I correct this?  This generally happens before I hit the "W" key to start the battle, when I notice that I have done something inadvertently wrong.

[Hook]

Press the F7 key and click on the Orders tab.  The orders are listed there, and you have the option to cancel them.

Hook

[Count von Csollich]

Press the F7 key and click on the Orders tab.  The orders are listed there, and you have the option to cancel them.

Does this only  work before one has started the game? Because if not, I wonder...Once you've sent a courier or an aide de camps with his order all you could do is send another one giving new instructions...so you had to be very careful in order not to confuse your commanders...