AS3, TextField Auto Scroll

As a beginner, I often ask questions.

I have a textfield with over 1000 music lists,
Only about 20 lines are shown in the textfield.
Is there a way to display the randomly selected music in the center of the textfield y-coordinate (or the 10th row)?
I would appreciate it if you could post the sample code to me.

for (var i: uint = 0;  i < sm.length;  i++)  {
	musicList.appendText(sm[i]+"\n");
}
var n: uint = int(Math.random() * (sm.length - 1));
musicPlay(sm[n]);