Problem with button

hello ladies and gentlemen))
there is a problem with my button.
here is my code:

 
stop();
_root.enter_btn.onRelease = function() {
 _root.up_mc.onEnterFrame = function() {
  _root.up_mc._alpha += 5;
  if (_root.up_mc._alpha>100) {
   _root.up_mc._alpha = null;
   delete _root.enter_btn.onRelease;
   delete _root.up_mc.onEnterFrame;
  }
 };
 _root.createEmptyMovieClip("login_cnt", 1);
 _root.login_cnt._x = 465;
 _root.login_cnt._y = 112;
 _root.login_cnt.attachMovie("loginForm", "loginForm_mc", 1);
};
_root.up_mc.onRelease = function() {
 _root.up_mc.onEnterFrame = function() {
  _root.up_mc._alpha -= 5;
  if (_root.up_mc._alpha<0) {
   delete _root.up_mc.onEnterFrame;
   delete _root.up_mc.onRelease;
  }
 };
 delete _root.enter_btn.onRelease;
 _root.login_cnt.removeMovieClip();
};

this code works only ONE time) the second time i’m pressing the button - no effect(
please help! i’m stuck(