Please override the $.fn.textbox.defaults.inputEvents.keydown event handler.
(function($){
$.extend($.fn.textbox.defaults.inputEvents, {
keydown: function(e){
if (e.keyCode == 13){
var t = $(e.data.target);
t.textbox('setValue', t.textbox('getText'));
var all = $('input:visible').not(':disabled').toArray().sort(function(a,b){
var t1 = parseInt($(a).attr('tabindex')||1);
var t2 = parseInt($(b).attr('tabindex')||1);
return t1==t2?0:(t1>t2?1:-1);
});
var index = $.inArray(this, all);
var nextIndex = (index+1) % all.length;
$(all[nextIndex]).focus();
}
}
})
})(jQuery);