My gameobject moves up wrong

I made a gameobject, and when you click on that gameobject it moves a bit up. and when you then click on it again ti moves a bit up again. And so on. But what it does it when it moves, it just go straight up. If it could go up smootlhy it would be nice, but how do i do that? Here is the script that i made: #pragma strict var speed:int = 5; function OnMouseDown () { transform.Translate(Vector3(0,speed,0) * Time.deltaTime); }