Is there a way to change unit's projectile speed using trigger

Topic:
See subject..
Hope someone will help me.
Thanks.

I actually think there is... By the use of items? Orbs have their own projectile speeds and models used...this might be the way to go..not sure though..

But won't you have to create many spells for all those with different projectiles?
It there a way to create a spell like "Slow Missile" in Diablo 2, rather than being like RazorClaw X in his KoS map which reduces the damage, is there a better way to change the projectile speed of a unit other than giving it the orb abilities?