Shooting at moving targets

[Vaxalon]

Ah, then what you want is something that allows you to take "fight defensively" in missile combat.

Something like...

The D20 rules!

From the SRD:

Attack (ranged) [Standard][AoO: Yes]

Description: The combatant attacks an opponent in line of sight to the combatant, within range of the ranged weapon being used.

.....

A combatant can choose to fight defensively when taking the attack action. If a combatant does so, the combatant takes a -4 penalty on all attacks in a round to gain a +2 dodge bonus to AC for the same round.