Centering attachMovies from different size Arrays

So, I have the following function…

buildLetter = function (x, y) {
tmpStrWord = wordArray[nextWord].word;
tmpStageArray = tmpStrWord.split("");
for (i=0; i<stageArray.length; i++) {
var currLetter = this.attachMovie(“mcLetter”, “mcLetter”+i, i);
currLetter._x = x+i*(currLetter._width+distanceApart);
currLetter._y = y-currLetter._height;
currLetter.txtLetter.text = stageArray*;

I need the attachedMovie clips to be centered on the stage no matter how long the array gets in terms of letters.

Oh and the size of letters cannot be scaled down.

Any ideas?