$(document).ready(function(){
     
     $(".carrito .cantidad").each(function(index){
        $(this).bind("keydown", OnlyNumber); 
     });
   
     function OnlyNumber(event) {
      
      var button = $(this).parent().parent().find("input[name*=btnCarrito]").attr("id");
      
      var keycode = (event.keyCode ? event.keyCode : (event.which ? event.which : event.charCode));
      
      if ( keycode == 46 || keycode == 8 ) 
      {
      }
      else if (keycode == 13) 
      {
         document.getElementById(button).click();
         
         return false;
      } 
      else if (event.keyCode < 95) { 
      
          if (keycode < 48 || keycode > 57) 
          {
            event.preventDefault();	
          }
      }	
      else if (keycode < 96 || keycode > 105 ) 
      { 
         event.preventDefault();	
      } 
      else  
      {
         return true;
      }
   }
});