window.onload = function() {
  var htmlselectobj = $$('#agenti select');
  showRegion(htmlselectobj[0].selectedIndex);

}

function showRegion(id) {
  var htmloptionsobj = $$('#agenti option');
  var choosenvalue = htmloptionsobj[id].value;
  var htmltableobj = $$('#agenti table');
  var allrows = htmltableobj.getElements('tr')[0];
  var selrows = htmltableobj.getElements('.'+choosenvalue)[0];
  for (i = 1; i < allrows.length; i++) { allrows[i].style.display = 'none'; }
  for (j = 0; j < selrows.length; j++) { selrows[j].style.display = ''; }
}