document.observe('dom:loaded', function() {
  applyPoBoxSearch();
});


function applyPoBoxSearch() {
  $$('.service_select').each(function(input) {
    input.observe('change', function(event) {
      var element = event.element();

      if (element.value == 'po_box') {
        window.open('https://poboxes.usps.com/poboxonline/search/landingPage.do', "_blank");
      }
    });
  });
}