function move () {
    this._x += 5;
    if (this._x >= 100) {
        delete this.onEnterFrame;
    }
}

stop ();

b_mc.onEnterFrame = move;
c_mc.onEnterFrame = move;
d_mc.onEnterFrame = move;
a_mc.onEnterFrame = move;

function move () {
    var nextTime = getTimer ();
    var diffTime = nextTime - startTime;
    if (diffTime >= 1000) {
        startTime = getTimer ();
        this._x += 5;
        if (this._x >= 100) {
            delete this.onEnterFrame;
        }
    }
}
stop ();

b_mc.onEnterFrame = move;
c_mc.onEnterFrame = move;
d_mc.onEnterFrame = move;
a_mc.onEnterFrame = move;