random object creation and there movement

i have created random object of type cube and when i run it gets created now i want those created objects to have motion in x and z axis,any on eof u know how to do that

Here is my code

var CubePrefab : GameObject;

var AmountOfCubes : int;

var RandomPosx : int;

var RandomPosy : int;

var RandomPosz : int; function Start() {

  for(var i=0;i<200;i++)
  {      
 if (AmountOfCubes <=200)
    {
 

RandomPosx = Random.Range (20,100);

RandomPosy = Random.Range (0,0);

RandomPosz = Random.Range (0,2042);

SpawnRandomCube(); } } }

// Move object using accelerometer variables

var speed = 1;

var movey=1;

function Update () {

  var dir : Vector3 = Vector3.zero;
 // we assume that device is held parallel to the ground
 // and Home button is in the right hand
 
 // remap device acceleration axis to game coordinates:
 //  1) XY plane of the device is mapped onto XZ plane 
 //  2) z plane has fixed value 1 which cause it to move in same direction 
 //but user can move in x direction with the phone acceleration sensor   
 dir.x =  Input.acceleration.x;
 dir.z = movey;
 
 // clamp acceleration vector to unit sphere
 if (dir.sqrMagnitude > 1)
     dir.Normalize();
 
 // Make it move 10 meters per second instead of 10 meters per frame...

// dir *= Time.deltaTime;

 // Move object
 transform.Translate (dir * speed);
 transform.Translate(0, 0, 1);

}

function SpawnRandomCube() {

transform.position = Vector3 (RandomPosx,RandomPosy,RandomPosz);

var RandomCube = Instantiate(CubePrefab,transform.position,transform.rotation);

AmountOfCubes = AmountOfCubes + 1;

}

now i have to move these cubes in z axis and if possible then in z axis.