Wait a specific time?

I want to have an object move upwards after 8 seconds have passed. I have a script, and it’s not working. Here’s the javascript:

//Whether it's waited or not
var dontchangethis : boolean;
//Set the variable to false
dontchangethis=false;
//Wait 8 Seconds
yield WaitForSeconds (8);
//Set the variable to true
dontchangethis=true;
//If the variable's true, then move upwards
function Update(){
	if (dontchangethis){
		transform.Translate(Vector3.up * (Time.fixedDeltaTime * 5));
	}
}

Any help?

Your code is right, but you have to be in a function for anything to happen. If you want to have it wait 8 seconds at start:

var dontchangethis : boolean; //this is a global variable
function Start(){
    //Set the variable to false
    dontchangethis=false;
    //Wait 8 Seconds
    yield WaitForSeconds(8);

    //Set the variable to true
    dontchangethis=true;
}

function Update(){
    if (dontchangethis){    //If the variable's true, then move upwards
       transform.Translate(Vector3.up * (Time.fixedDeltaTime * 5));
    }
}