Event.observe(window, 'load', function (event)
{
    var updateScreenName = function()
    {
        var setResult = function(transport)
        {
            $('register_screen_name').value = transport.responseText;
        };

        new Ajax.Request('../register/screenName', {method: 'get',
                                                                               parameters: {'first': $('register_first_name').getValue(),
                                                                                                       'last': $('register_last_name').getValue()},
                                                                               onSuccess: setResult});
    };
    $A([$('register_first_name'), $('register_last_name')]).each(function(item) {
        item.observe('change', updateScreenName);
    });
});