ActionScript 3.0 :: Slider To Change Height Of Silhouette?

I am trying to build a interactive slider,in which when user drag the slider up the height of silhouette increases by some fix amount n when user drag the slider down the height of silhouette decreases by some fix amount.the problem i am facing is that when i drag the slider slowly than everything works fine but when i drag the slider faster than the height dont increase or decrease properly.i mean the increment or decrement in the height of silhouette is depending on speed of slider,which i dnt want.

here is the code-

Code:
var bounds:Rectangle = new Rectangle(499.65,260,0,240);
slider.addEventListener(MouseEvent.MOUSE_DOWN, moveSlider);
stage.addEventListener(MouseEvent.MOUSE_UP, stopSlider);

[code]....