Setinterval doesn't loop back

[digitalecartoon]

I want to make a clip expand/shrink upon rolling over/out of a button. Also I want to control its expanding/shrinking speed, so I'm using setinterval for this. This code kinda works, but only while expanding to yscale 300. When I rollout it should shrink back to 0 again, but it looks like it jumps back and forth from 290 to 300. What am I doing wrong?

var i:Number = 0;
function Increase() {
    if (i<=200) {
        clip._yscale = i;
        i = i+20;
    } else {
        clearInterval(nInterval);
    }
}
function Decrease() {
    if (i>0) {
        clip._yscale = i;
        i = i-20;
    } else {
        clearInterval(nInterval);
    }
}
//
button.onRollOver = function() {
    var nInterval:Number = setInterval(Increase, 20);
};
button.onRollOut = function() {
    var nInterval:Number = setInterval(Decrease, 20);
};

[dawsonk]

var nInterval:Number;
button.onRollOver = function() {
	clearInterval(nInterval);
	nInterval = setInterval(Increase, 20);
};
button.onRollOut = function() {
	clearInterval(nInterval);
	nInterval = setInterval(Decrease, 20);
};

[digitalecartoon]

I thought of that myself but it doesn't work. Tried it with this:

var i:Number = 0;
Increase = function () {
	trace(i);
	i = i+20;
};
Decrease = function () {
	i = i-20;
};
//
var ID:Number;
button.onRollOver = function() {
	clearInterval(ID);
	ID = setInterval(Increase, 20);
};
button.onRollOut = function() {
	clearInterval(ID);
	ID = setInterval(Decrease, 20);
};

But what it does when I rollover the button is it goes from 0 to up (so far so good), but on rollout I cleared the interval and started a new one which should decrease it again. But for some reason the Increase function keeps on working.

So when I have in increased to 200 and do a rollout, it should start the Decrease function. Not tracing a value but just decreading the variable. But instead the Increase function keeps working and continuously traces 200.

Why???

[dawsonk]

Still need to keep the clearIntervals in the Increase and Decrease functions.

var i:Number = 0;
function Increase() {
	if (i <= 200) {
		clip._yscale = i;
		i = i + 20;
	} else {
		clearInterval(nInterval);
	}
}
function Decrease() {
	if (i > 0) {
		clip._yscale = i;
		i = i - 20;
	} else {
		clearInterval(nInterval);
	}
}
//
var nInterval:Number;
button.onRollOver = function() {
	clearInterval(nInterval);
	nInterval = setInterval(Increase, 20);
};
button.onRollOut = function() {
	clearInterval(nInterval);
	nInterval = setInterval(Decrease, 20);
};