All you can do is compare the sprites angle to make sure it doesn't go above or below.
I compare the sprites angle, look at the this screenshot:
<img src="http://d.imagehost.org/0528/images_1.png">
Maybe I'm doing something wrong. If so, tell me please how to make the correct event that would compare the angles and the circle would move without jerks?
Is there any plugin?
Or this program cannot to make a simple volume control controlled by the mouse?
<img src="http://d.imagehost.org/0802/bad_stan.png">