Object moving to one point and back

Hello,

How can I make that cube will move forward and back automaticlly?
Sorry for my bad english

bye

 

var startPos : Vector3;
var distance : float;

function Awake ()
{
startPos = transform.position;
}
function Update ()
{
transform.position = startPos+Vector3(Mathf.Sin((1/distance)*Time.time),0,0);
}

Not completely sure what you want, but here's something to play around with. Make the direction you want to go one of the values on the Vector3
Hope this helps!