var Tickets = {
    category : null,

    init : function() {
        Tickets.category = $('id_category');
        if (Tickets.category) {
            Tickets.category.onchange = function() {
                Tickets.redirect();
            }
        }
    },

    redirect : function(event) {
        if (Tickets.category.selectedIndex && (start = Tickets.category.options[Tickets.category.selectedIndex].value.indexOf('http://')) > -1) {
            window.location = Tickets.category.options[Tickets.category.selectedIndex].value.substr(start);
        }
    }
};