[F8] SetInterval is driving me insane!

Allright, Im certain I am doing just ONE thing wrong here thats making flash crash everytime I test this and not making setInterval work properly, if anyone could point it out it would be great. I need it for a website for a client and I’ve been racking my brains out trying to figure out what I am doing incorrectly. Everything works out ok except when I try to incorporate setInterval into my code, then I run into issues again.

on (rollOver) {
    var myInt:Number;
    var playIt:Number;
    var i:Number = 45;
    var i = 45;
    myInt = setInterval(playIt, 3);
     function playIt() {
        while (i>0) {
            var scroller = scroller+1;
            var i = i-1;

Anyway, thanks in advance for the help. Im still new to actionscript so I am trying my best at this.