Some segments in a URL

[eluser]Ayelius Maximous[/eluser]
Hi guys
Forgive me if my English is not well.
Before I start using CI, I used manual url for my project, for example this was one of my url's :

Code:

http://localhost/my-project/admin/settings.php?set=sgmnt&act=add&stp=1/

and in setteings.php I had codes bellow:

Code:

if($_GET['set'] == 'sgmnt' && $_GET['act'] == 'add' && $_GET['stp'] =='1')
    add_segment_stp1();

else if($_GET['set'] == 'sgmnt' && $_GET['act'] == 'add' && $_GET['stp'] =='2'){
    add_segment_stp2();
}

and now in CI I need URL's like this one.
In my CI project, I have a controller named Segments.php in location : application\controllers\Admin
and in controller :

Code:

class Segments extends CI_Controller {
function Lst(){
  $data = array(
  'title' => "سیستم جامع » پنل مدیریت » لیست مقاطع"
  );
  $this->load->helper(array('html', 'url', 'date'));
  $this->load->model('Admin/Segments_Model');
  $this->load->view('Admin/header', $data);
  $this->load->view('Admin/Segments/Lst');
  $this->load->view('Admin/footer');
  }
  function add(){
  $data = array(
  'title' => "سیستم جامع » پنل مدیریت » افزودن مقطع"
  );
  $this->load->helper(array('html', 'url', 'date', 'form'));
  $this->load->model('Admin/Segments_Model');
  $this->load->view('Admin/header', $data);
  $this->load->view('Admin/Segments/Add');
  $this->load->view('Admin/footer');
  }
}

So I can use this URL :

Code:

http://localhost/ci/index.php/Admin/Segments/Add

But I need to use sub-segments in Add function like my previous programing method, like switch function that I can define some cases.
like this one:

Code:

http://localhost/ci/index.php/Admin/Segments/Add/1/2

I read CI user guide, but because of my bad English I couldn't understand what should I do?
If you can with example tell me what should I do?