Duplicate movieclip holder

hey guys i sent up a question for a lego game3 weeks ago – i got the game to work splendid thanks guys

heres the link–

i have a question though
–They duplicate and stuff but i want it to stop duplicating if the previous clip is not moved from where it was duplicated

heres the code im using to duplicate the movieclips

on (release) {
music = new Sound();
music.start(0, 1);
if (i<900) {
duplicateMovieClip("_root.box3red", “box3red”+i, i);
_root[“box3red”+i]._x = random(30)+50;
_root[“box3red”+i]._y = random(60)+50;
_root[“box3red”+i].onRelease = function() {
delete this.onMouseMove;