How do you make random local velocity for particles?

I'm pretty new to Unity and found I couldn't make the particle effect I was going for (using a particle emitter component) without random local velocity. My first thought was to make a script adding values which would translate to world values then be added to the existing rndVelocity options. I can't figure out how to do it though. This is what I tried:

var rndLocalVelX : float = 0;
var rndLocalVelY : float = 0;
var rndLocalVelZ : float = 0;
var particlez : ParticleEmitter;
var relativeDirection : Vector3;

function Start ()
    var randomAdd : Vector3; 
    randomAdd = Vector3(

    relativeDirection = transform.TransformDirection(randomAdd);

    particlez = GetComponent(ParticleEmitter);

    //adding a random value to local velocity:
    particlez.rndVelocity += relativeDirection;

I don't understand what you're trying to do, but anyway, the variable called `Rnd Velocity` is already local random velocity. So you can just set that value directly.

do you need to add positive and negative velocity? If so, use Random.Range(min, max)

randomAdd = Vector3(Random.Range(-rndLocalVelX, rndLocalVelX), Random.Range(-rndLocalVelY, rndLocalVelY), Random.Range(-rndLocalVelZ, rndLocalVelZ));

you would set this as Velocity instead of rndVelocity ofcourse