Tween not working inside function

Hi
I really can’t work out why this isn’t working
Once i take the tween out of the function it works
[AS]
container.alpha = 0;

container.addEventListener(Event.ENTER_FRAME, tweenUp);
function tweenUp(evt:Event) {
if (folder.currentFrame == 11) {

tweenInGallery()

}
}
function tweenInGallery() {
var alphaTween:Tween = new Tween(container, “alpha”, None.easeInOut, 0, 1, 5, true);
}
[/AS]