randomize particle path

Hey guys, i am trying to make a lightning effect. So far i manager to access my particles (shuriken) with a script. How could i change the path of my particles ¿

Just create the particle effect and put random values in for its starting position.

lightningObject.position = new vector3(Random.range(low, high), Random.range(low, high),Random.range(low, high));

I want to access the velocity over lifetime. want to change the values every 10 Frames for example. That way i guese i will get a relistic lightning.

How to access this value (if it is accessable trouh a script).