[Nutrox]

 
The following function will allow you to align movie clips horizontally or vertically. You can also set the amount of spacing between each movie clip.

function alignClips(clips:Array, alignment:String, spacing:Number):Void {
    if (spacing == null) {
        spacing = 0;
    }
    var hori:Boolean  = alignment == "horizontal";
    var propA:String  = hori ? "_x" : "_y";
    var propB:String  = hori ? "_y" : "_x";
    var length:String = hori ? "_width" : "_height";
    var value:Number  = clips[0][propA];
    var i:Number      = 0;
    var n:Number      = clips.length;
    
    while (i < n) {
        clips[i][propA] = value;
        if (i) {
            clips[i][propB] = clips[i-1][propB];
        }
        value += clips[i++][length] + spacing;
    }
}
 
// Create an array and populate it with the movie clips
// that we want to align.
var myClips:Array = [mc1, mc2, mc3, mc4];
 
// Align the movie clips horizontally with 10px spacing.
alignClips(myClips, "horizontal", 10);
 
// or.. Align the movie clips vertically with 2px spacing.
// alignClips(myClips, "vertical", 5);