Start MC with mouse position

I’m trying to make a movie clip play when the mouse is in a certain position on the screen without using invisible buttons, coding this myself so far I’ve got

_root.top = 319
_root.bottom = 445
yval = _root._ymouse;
if (_root._ymouse > _root.top) {
_root.flowers.play();
} else {
_root.flowers.stop();
}

doesn’t seem to work right.

Any ideas?