In my game i have 4 pistons set up, they raise and lower themselves and you have to jump from one to another. To raise them and lower them i have this script set up:

private var startPoint : Vector3;
var endPoint : Transform;
var duration : float = 5.0;
private var startTime: float;
private var Point2: Vector3;
private var position2 : boolean = false;
private var number1: int = 0;
private var number2: int = 0;

function Awake(){
startPoint = transform.position;
Point2 = endPoint.position;
startTime = Time.time;
}
function Update () {
if(number1 ==1){
startTime = Time.time;
}
if(number2 ==1){
startTime = Time.time;
}
if(position2){
transform.position = Vector3.Lerp(Point2, startPoint, (Time.time - startTime) / duration);
} else {
transform.position = Vector3.Lerp(startPoint, Point2, (Time.time - startTime) / duration);
}
if(transform.position == Point2){
number1 +=1;
number2 = 0;
position2 = true;
} 
if(transform.position == startPoint){
number2 +=1;
number1 = 0;
position2 = false;
}

}

Well they raise and lower just fine and that works out, but if you stand on them and dont move when a piston raises you just stay at that height, until you go through it, then you fall. Though, when you move you raise up with it, is there a way to make it constantly push you up, like riding an elevator (hence the name of the question)?