SWISH.
I have invented Santh's Schizophrenic Seeker-Swarmers
On Created
Pick nearest Enemy to (Player.X, Player.Y)
IF Enemy.Targeted = 0
[Set Missile.Target to Enemy.UID]
[Set Enemy.Targeted to 1]
ELSE
WHILE
Missile.Target = 0
Pick a random Enemy instance
IF Enemy.targeted = 0
[Set Missile.Target to Enemy.UID]
[Set Enemy.Targeted to 1]
This means that the missiles will target the closest enemy, unless it has already been targeted, in which case they will target a random untargeted enemy.
It's a pretty decent effect. Especially when fired in bursts. Still needs some fine tuning though.
Thanks for your help!