Masking with external loaded MC

guys any of you have any idea how to achieve this?
I have 16 movie clips on stage and i want all of them to be masked with another movieclip from the library.

here’s the script i use, but it’s all just rough guess, it needs major modification:

[AS]
import flash.filters.DropShadowFilter;
var drop:DropShadowFilter = new DropShadowFilter(0, 45, 0x000000, .6, 5, 5, 1, 1, false, false, false);
for (var i = 1; i<17; i++) {
this[“mc”+i].onEnterFrame = function() {
this.filters = [drop];
this.attachMovie(“maskIN”, “mask”, 0, {_x:this, _y:this});
this[“mc”+i].setMask(mask);
};
this[“mc”+i].onRollOver = function() {
mask.gotoAndPlay(2);
};
this[“mc”+i].onRollOut = function() {
mask.gotoAndStop(1);
};
}
[/AS]

anyways here’s an attachment, please help!