[bicubic_bublic]

предлагаю такой вариант:

<script type="text/javascript">
window.onmousemove = function(e) {
   e = e || window.event; // для старых версий IE
   window.mousePosition = { x: e.screenX, y: e.screenY };
}
</script>

во флеше

var mousePosition:Object = ExternalInterface.call('function () { return window.mousePosition; }');