var ref = '';

function ajax_request(url,data,target,cb_func){
   clearTimeout(ref);
   new Ajax.Request(url, {
      method: 'get',
      parameters: data,
      onSuccess: function(transport) {
         if(target){
            $(target).innerHTML = transport.responseText;
         }
         if(cb_func){
            ref = setTimeout(cb_func,2000);
         }
      }
   }
);
}