Much to my chagrin, I once again find my self unable to effectively command large forces in a Total War game. When I deploy my army into a custom formation - let's say, for the sake of argument, archers in a thin line at the front, then heavy infantry, then cavalry off-centre, then light infantry in reserve - then select them all and order them to move approx. a bow's shot from the enemy army, they all just mass up into one big mish-mash of a line. How do I prevent this?

Also - how do I order my archers to stop firing (used when the melee has been joined and I don't wanna hit my own guys). I've tried both disabling 'Fire at Will' and hitting Halt, but neither seems to have any affect.