[etc]

function s_Buffer(id, x, y) {
	this._mc = _root.attachMovie(id, id + _global._lowerLevel, _global._lowerLevel, {_x:x, _y:y, buffer:this});
}

s_Buffer.prototype.receiveChildMessage = function(msg) {
	trace(msg);
}

var testBuffer = new s_Buffer("test", 10, 10);

this.buffer.receiveChildMessage("test");