Adding a _mc that loads my swf's center

1

I’m using this code

// ***Stage aligned top left
Stage.align = "TL";
// *** Stop the stage from scaling with the browser window.
Stage.scaleMode = "noScale";
stop ();
// initiate postitions and scaling values for objects
bottomstretch._height = Stage.height;
rightstretch._height = Stage.height;
topstretch._width = Stage.width;
rightstretch._x=201;
otherstretch._width = Stage.width;
// end initial position setting


//create a listner that checks to see if the browser window is resized
sizeListener = new Object();
sizeListener.onResize = function() {
    // change movieclip properties when the window is resized.
    topstretch._width = Stage.width;
    otherstretch._width = Stage.width;
    bottomstretch._height = Stage.height;
    rightstretch._height = Stage.height;
    //*note* 200 is the width of the left column
    audio._x = Stage.width - audio._width
};
Stage.addListener(sizeListener);

having trouble adding a _mc that loads my swf’s center, always nomaterr screen size.

Anyone know how this can be tweeked?