Simulando nth-child com jquery

index.html

<div class="page-group">  
           <div class="page"></div>  
           <div class="page"></div>  
           <div class="page"></div>  
      </div>

script.js

 <script>  
 $(document).ready(function(){  
      var cont = 1;  
      $('.page').each(function(){  
           if((cont%3)==0){  
                $(this).css({'margin-right':'0px'})  
           }  
           cont = cont +1;  
      });  
 });  
 </script>

style.css

.page-group{float:left; width:960px;}  
.page{float:left; width:306px; height:330px; background:#09C; margin:15px 20px 0 0;}