Move empty object random

I have to move an empty object every 3 seconds randomly within a defined area. to do this, I created this script:

pragma strict

var Spaw: GameObject;

function Start () {

}

function Update () {

transform.position = new Vector3 (Random.Range (-25.0f, 25.0f, 0.0f, 130.0f, 135.0f));

}

But it does not work.
where did I go wrong?

Here is a more complete answer for you now I have a bit more time.

function Start () {

    //The "0" say to start this right now. The "3" says to repeat this every three seconds.
    InvokeRepeating("subMove_Object", 0, 3);
}

function subMove_Object() {

    transform.position = Vector3((Random.Range(-25.0, 25.0), 0.0, Random.Range(130.0, 135.0));
}