change variable in runtime

Hi,

My code must work for random variable in random time.
or in other words I want change a random variable in runtime but It will change at end of every ten seconds(or in random time) ?
i could not.

How can i add random time for change variable in runtime?

#pragma strict


public static var spdGrupOne = Random.Range(12,18);

function Start () {

}


function Update () {

    Debug.Log(spdGrupOne);

}

Problem solved.
thanks