jQuery(document).ready(function($) {
   textboxes = $("#cartForm input:text");

   if ($.browser.mozilla) {
      $(textboxes).keypress(checkForEnter);
   } else {
      $(textboxes).keydown(checkForEnter);
   }

   function checkForEnter(event) {
      if (event.keyCode == 13) {
         currentTextboxNumber = textboxes.index(this);

         if (textboxes[currentTextboxNumber + 1] != null) {
           nextTextbox = textboxes[currentTextboxNumber + 1];
           nextTextbox.select();
      }

         event.preventDefault();
         return false;
      }
   }
});