Masking multiple attached movieclip

hai all,

i am using Flash MX2004(AS 2.0), i need to mask the attached movieclip,
totally i attached 3 movieclip(all are same one), i need to display first movieclip by using mask. one more thing is moving that mask by press button, when i press the button the mask will show the second movie clip and so on…can any one help me…

this is my code:i have to mask box1_mc

function cardcolor() {
var color:Color = new Color(_root[“box_mc1”+i].box1_mc);
var t:Number = 0x00FF00;
_root[“box_mc1”+i].onPress = function():Void {
if (t == 0x00FF00) {
color.setRGB(0x0000FF);
} else if (t == 0x0000FF) {
color.setRGB(0x00FF00);
}
color.getRGB();
t = color.getRGB();
};
}
var x1 = 100;
for (var i = 1; i<=3; i++) {
_root.attachMovie(“box_mc”,“box_mc1”+i,i);
cardcolor();
_root[“box_mc1”+i].setMask(mask_mc);
_root[“box_mc1”+i]._x = x1;
_root[“box_mc1”+i]._y = 100;
x1 += 200;
}

thanks…
sakthimani(-: