You can do that with DeltaPitch and DeltaYaw.
DeltaPitch tells you if the target is above (+) or below (-) the missile.
DeltaYaw is used to determine whether the target is to the left (-) or right (+) of the missile.
So for example, if DeltaYaw returns -10, you know that your missile needs to turn to the left. If DeltaPitch returns 40 then you need to increase the pitch of the missile.
If DeltaPitch and DeltaYaw were both 0, (which is not likely since they both return floats, but it keeps the explanation simple), then the missile is pointing directly at the target object.
Hope this helps.
[Edit] As for DeltaRoll - you don't need this. Just keep your EntityRoll for the missile at zero. Can do that with RotateEntity missile,EntityPitch(missile),EntityYaw(missile),0[,true]
DeltaPitch tells you if the target is above (+) or below (-) the missile.
DeltaYaw is used to determine whether the target is to the left (-) or right (+) of the missile.
So for example, if DeltaYaw returns -10, you know that your missile needs to turn to the left. If DeltaPitch returns 40 then you need to increase the pitch of the missile.
If DeltaPitch and DeltaYaw were both 0, (which is not likely since they both return floats, but it keeps the explanation simple), then the missile is pointing directly at the target object.
Hope this helps.
[Edit] As for DeltaRoll - you don't need this. Just keep your EntityRoll for the missile at zero. Can do that with RotateEntity missile,EntityPitch(missile),EntityYaw(missile),0[,true]