Simple question concerning mouse trailer

Hello. I am playing around with the Kirupa mouse trailer tutorial, and I am trying to make it so that at different points along a M.C. different pieces of text start following the mouse…a button plays a specific part of the m.c. in which the “trailer code” (pasted below) is, when the user clicks a different button, the playhead goes to a different part of the m.c. that has the same “trailer code” within it, but with different text…Everything is working except when you click the buttons in reverse order a some of the letters from one text are attached the other piece of text. I think I need to clear a variable or something, but am unsure. I know this sounds confusing, but if anyone could help I would appreciate it.
The piece of code is:
delete (Text);

Text = “first text”;
letters = Text.split("");
letterformat = new TextFormat();
letterformat.font = “Papyrus”;
letterformat.align = “center”;
letterformat.size = “8”;
spacing = 5;
speed = 3;
for (var LTR = 0; LTR<letters.length; LTR++) {
mc = _root.createEmptyMovieClip(LTR+“l”, LTR);
mc.createTextField(letters[LTR]+“x”, LTR, LTR*spacing, 10, 20, 20);
with (mc[letters[LTR]+“x”]) {
text = letters[LTR];
setTextFormat(letterformat);
selectable = false;
}
if (LTR) {
mc.prevClip = _root[(LTR-1)+“l”];
mc.onEnterFrame = function() {
this._x += (this.prevClip._x-this._x+5)/speed;
this._y += (this.prevClip._y-this._y)/speed;
};
} else {
mc.onEnterFrame = function() {
this._x += (_root._xmouse-this._x+10)/speed;
this._y += (_root._ymouse-this._y)/speed;
};
}
}