Function problems

1

I am new at flash and teaching myself and was wondering why this function won’t work.

 
// initialize
links_mc.link1_mc._alpha = 30;
links_mc.link2_mc._alpha = 30;
links_mc.link3_mc._alpha = 30;
// call function
links_mc.link1_mc.link_btn.onLinks(links_mc.link1_mc.link_mc, 70, 30);
// function
MovieClip.prototype.onLinks = function(link_mc, start_alpha, end_alpha) {
  this.onRollOver = function() {
	link_mc._alpha = start_alpha;
  };
  this.onReleaseOutside = function() {
	link_mc._alpha = end_alpha;
  };
  this.onRelease = function() {
	link_mc._alpha = end_alpha;
  };
  this.onRollOut = function() {
	link_mc._alpha = end_alpha;
  };
};