Help with in-game animations (effects)

[bnw2000]

Ive seen some games use effects for guns and i would like to know how do i attach the muzzle fire effect to the gun when a unit attacks.

I think if u do the trigger below, it may have some leaks.

rifleman
Events
Unit - A unit Is attacked
Conditions
(Unit-type of (Attacking unit)) Equal to Rifleman
Actions
Unit - Add (custom skill with effect) to (Attacking unit)

then u just remove it if he doesnt attack....HOWEVER , if the unit missle would be slow if i want to show the projectile... wouldnt the effect be "lagging" behind maybe lets say... 1 second???

How do i make a trigger to do that? If you guys have JASS to do this , could you show it to me? ( teach me how 2 do use it too , im 0% good with JASS)