Volume Control

1

HI everyone, im working on a volume control slider with the following code:
this.ratio = 0;

dragger.onPress = function() {
 this.startDrag(true, 0, 0, line._width, 0);
 this.onEnterFrame = function() {
  ratio = Math.round(this._x*100/line._width);
  _root.volume = ratio;
 };
};
dragger.onRelease = dragger.onReleaseOutside=stopDrag;

how can you make it start at half volume?