as3 Changing dynamic text in a symbol - actionscript-3

Question

I have a symbol tile with multiple keyframes. One of the keyframes has a dynamic text box with the instance name pTwo.
I want to change the text in pTwo to an empty string and have tried:
pTwo.text = String(""); //Atempt One
MovieClip.pTwo.text = String(""); //Attempt two
Any help would be appreciated. Thanks in advance
EDIT: Im making a tile game and using an array to make the map - my array is as follows:
public var myMap: Array = [
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
[1, 0, 0, 0, 3, 2, 2, 2, 0, 1],
[1, 0, 0, 0, 0, 0, 2, 0, 0, 1],
[1, 0, 2, 0, 2, 0, 0, 0, 0, 1],
[1, 0, 2, 2, 0, 3, 0, 0, 0, 1],
[1, 0, 0, 0, 0, 0, 2, 2, 0, 1],
[1, 0, 2, 0, 2, 0, 2, 0, 0, 1],
[1, 0, 2, 2, 2, 0, 2, 0, 2, 1],
[1, 0, 0, 0, 0, 0, 2, 0, 0, 1],
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1]
];
All the arrays are made from the symbol called 'tile' which consists of different key frames. So each number in the array references a different key frame. I have a character and when the character walks over the tile- I want the dynamic text to change to empty to imitate an empty tile- alternatively if theres a way to replace the tile with a [0] , that would also be good.
my code that generates the board:
var mapWidth = 10;
var mapHeight = 10;
var tileSide = 32;
var totalTiles = mapWidth * mapHeight;
var myMap: Array = [
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1],
[1, 0, 0, 0, 3, 2, 2, 2, 0, 1],
[1, 0, 0, 0, 0, 0, 2, 0, 0, 1],
[1, 0, 2, 0, 2, 0, 0, 0, 0, 0],
[1, 0, 2, 2, 0, 3, 0, 0, 0, 1],
[1, 0, 0, 0, 0, 0, 2, 2, 0, 1],
[1, 0, 2, 0, 2, 0, 2, 0, 0, 1],
[1, 0, 2, 2, 2, 0, 2, 0, 2, 1],
[1, 0, 0, 0, 0, 0, 2, 0, 0, 1],
[1, 1, 1, 1, 1, 1, 1, 1, 1, 1]
];
for (var i: int = 0; i < mapHeight; i++) {
for (var u: int = 0; u < mapWidth; u++) {
var cell: MovieClip = new tile();
cell.gotoAndStop(myMap[i][u] + 1);
cell.x = tileSide * u;
cell.y = tileSide * i;
addChild(cell);
};
};
Sorry i was not clear from the start. New at actionscript so i apologise in advance if my terminology is unclear.

Answer 1

Is this "tile" symbol available in all frames? If the playhead is moving, then the symbols within the MovieClip may become dereferenced. Add the "pTwo" object to your Watch list in debug and determine if it object exists as the "tile" symbol plays.
You may need to create a single frame symbol with 2 layers. One with the animated symbol and the other with the text.

Answer 2

If the TextField only exists on a particular frame, and you're sure that it's the current frame, you can use this:
TextField(getChildByName("pTwo")).text = "";
If you're not always sure, just wrap it in a try block:
try {
TextField(getChildByName("pTwo")).text = "";
} catch(error:Error) {
trace("text field doesn't exist on this frame");
}
If pTwo lives inside of a Movieclip, the code might look something like this:
try {
TextField(YourMovieclipsName.getChildByName("pTwo")).text = "";
} catch(error:Error) {
trace("text field doesn't exist on this frame");
}
Hope this helps!
Edit based on new info:
for (var i: int = 0; i < mapHeight; i++) {
for (var u: int = 0; u < mapWidth; u++) {
var cell: MovieClip = new tile();
cell.gotoAndStop(myMap[i][u] + 1);
cell.x = tileSide * u;
cell.y = tileSide * i;
try {
TextField(cell.getChildByName("pTwo")).text = "";
} catch(error:Error) {
trace("text field doesn't exist on this frame");
}
addChild(cell);
};
};