jquery scroll down with change letter spacing

jquery scroll down with change letter spacing

i want to animate text with scroll down.

i apply this code.this is working. but scrolled<400 not stop.code is running.how to fixed this issue,

Thank You .....
  1. $(function(){
    $(window).scroll(function() {
            var scrolled=-($(window).scrollTop())/50;
            
            $('#scrolled').text('scrolled: '+scrolled+'px'); 
          if(scrolled<400){ $('#cName').css({'letter-spacing':12+scrolled+'px'}); }
          else{$('#cName').css({'color':'red'});}
       });
        
    });