Use a boolean variable as a flag to indicate if the door is closed, and only open it if this flag is true:

var dooropenandclose : AnimationClip; //this is your animation clip.
var Celldooropensound : AudioClip;
var door : GameObject; //this is your game object that you want to move on trigger.
private var closed = true; // door initially closed

function OnTriggerEnter(){
    if (closed){ // only do it if door closed
        closed = false; // door now is open
        animation.Play ("dooropenandclose");
        audio.PlayOneShot(Celldooropensound);
    }
}