Timer event doesn't listen to my if else statements how do stop it?

Question

So I'm building a random generator of just a vector that i imported into flash and everything works just fine, almost. I added a timer to the creation of the vector. I also have some if else statements that are going to govern User Input. I realized that if the UI was initially outside of the parameters i've set it runs fine but once the once the function with the timer starts it never stops regardless of whether or not the UI is in the parameters I set. How do I stop the function when the UI is not what i want it to be?
Heres my code:
//initial universal variable declaration
var kface:Kobbyface;
var UI:Number;
var kfacex:Number;
var kfacey:Number;
var UIold:Number = 0;
var timer:Timer = new Timer(200);
//background rectangle
graphics.beginFill(0xFFFF00, 1);
graphics.drawRect(0,65, stage.stageWidth, stage.stageHeight);
graphics.endFill();
trace (inputnumber);
//eventlistener for click
gobutton.addEventListener(MouseEvent.CLICK, create);
function create(me:MouseEvent):void {
UI = Number(inputnumber.text);
if (isNaN(UI)) {
errormessages.text = "Kobby only responds to numbers"
else if (UI > 500) {
errormessages.text = "You're not ready for that many Kobbys"
else if (UI < 15) {
errormessages.text = "Come on you can handle more than that"
else{
createfaces();
//for loop///
function createfaces ():void {
////////timer for face animation///////
timer.addEventListener(TimerEvent.TIMER, animate);
timer.start();
function animate(evt:TimerEvent):void {
/////keep track of old number/////
if (UIold != 0) {
for (var i: int = 1; i<UIold + 1; i++) {
stage.removeChildAt(1);
    /////assign old number to new number////
UIold = UI;
for ( var i:int = 1; i<UI + 1; i++ ) {
trace( i );
////assign values to coordinate varialbes/////
var kfacex:Number = Math.random() * stage.stageWidth;
var kfacey:Number = Math.random() * stage.stageHeight + 65;
//creation of faces///
kface = new Kobbyface();
stage.addChild(kface);
kface.x = kfacex;
kface.y = kfacey;

Answer 1

you can apply the stop() method to your timer:
timer.stop();