Problem using xss_clean()

[eluser]stormlead[/eluser]
Hi all!
i want to use a form validation in which i just want to check the possible cross site script in the field. for which i am using the function as below

Code:

function username_check($name)
    {
      if($name=='')
      {
       $this->form_validation->set_message('username_check', 'The field can not be blank');
       return FALSE;
      }
      elseif ($this->input->xss_clean($name, TRUE) === FALSE)
      {
    // file failed the XSS test
       $this->form_validation->set_message('username_check', 'The field can not be blank');
       return FALSE;
       }
      else
      {
        return TRUE;
      }
    }

but the field is getting cleaned and i am getting output as

[removed]alert('in');[removed]

i just want to display a error message and not to process the field any further.
Please help me out to solve this ....