hey could anyone help me?

i’ve been set an assignment to create a city scene using actionscript only (see attatched file). i’m just wondering if someone could help me to make stars come out as night time falls, as this is a part of the assessment.

i have the following code but cannot get it to work:

var numStars:Number = 50; for (i=1; i<=numStars; i++)
{ _root[“star”+i].onEnterFrame = function()
{ this._alpha = Math.random()*40+60;