If Scale is less than

So Im making a script to scale an object. I want to know how I can so if the scale is less than 17.00, it will stop scaling.

var minValue : float = 17.0;
var maxValue : float = 200;
var scale : float;

function Update(){
  transform.localScale.x = scale;
  transform.localScale.y = scale;
  transform.localScale.z = scale;
}

function OnGUI(){
   scale = GUI.VerticalSlider (Rect (25, 25, 30, 250), scale, maxValue, minValue);
}