Dragging a slider along the y-axis between fixed positions

1

Hi, I’ve got the following situation:

In my flash application I want to slide a button on the y-axis of a kind of thermometer, but I want to establish fixed slider positions so you can only move the slider up and down from fixed position to fixed position.

I already use this bit of code with startDrag and stopDrag behaviours:

on (press) {
	startDrag ("_root.schuif",true ,245 ,190 ,245 , 480)
	var h
	var v
	h = schuif._x;
	v = schuif._y;
	x = 0;
	var y;
	y = y+50;
	_root.schuif._y = y;
}

on (release) {
	stopDrag ();
	if (_root.schuif._droptarget == "/opdracht") {
		loadMovieNum("geluid.swf",1);
		play();
	}
	
	}

Any help is much appreciated!
Many thanks in advance