Setinterval doesn't loop back

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?

Code:

---

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);
};

---

Code:

---

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

---

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

Code:

---

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???

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

Code:

---

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);
};

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