Stuck with simple show / hide dynamic text?

I am stuck with this

I want a simple dyn. texfield go down change text go up again. This all behind a mask


var payoffArray:Array = ["THis would be no 1", "Another payoff"];
var lineMC:MovieClip;
var payoffsMC:MovieClip;
function iniPayoffTxt() {
	payoffsMC.payoffTxt.text = "THis would be no 1";
}
function movePayoff() {
	trace("payoff _y: "+payoffsMC._y);
	trace("line _y: "+lineMC._y);
	if(payoffsMC._y < lineMC._y) {
		payoffsMC.onEnterFrame = goDown;
	} else {
		trace ("payoff > line");	
		clearInterval(testInt);
		delete this.payoffsMC.onEnterFrame;
		//show next payoff text

		//here come the go up after x sec
		payoffsMC._y = 15;
	}
}
function goDown() {
	this._y += 10;
}
function goUp() {

}
function showNextPayoffText() {
	testInt = setInterval(movePayoff, 5000);
}
iniPayoffTxt();
testInt = setInterval(movePayoff, 5000);

Any advice