ActionScript 3.0 :: Random Number Push Array

i have been racking my head for days over random number no repeats

iam doing a bingo caller game iam stuck with random number with no repeats this is the code snipplet im using

Code:
var num:Number = Math.ceil(Math.random()*90);

i use the timer class to call a number every few seconds

how do i do it with no repeats,

do i have to put the numbers into a array then pull the numbers from the array, here is some code i have found but can't get it to work

Code:
var firstarray:Array = new Array();
for(var u:Number = 1; u <= 90; u++){

[Code].....