Thanks, but that's not what I meant... I admit I was rather unclear!

If you have a number of units grouped and then select an enemy unit to attack, they do not necessarily attack the unit you selected. Rather they "line off" against the enemy, so they fire / charge at not just that single enemy unit but also at the enemy units next to it. What I want is to tell all my guys to attack a single enemy unit, rather than the enemy line. I was sure I heard about a key that you can hold whilst clicking the enemy unit that achieves this.

Is that any clearer?