Private function and Custom form validation

[eluser]BenAbrams[/eluser]
Hi Guys

I have a custom field validation rule in a config file set up, something similar to to the below:

Code:

array(
     'field' => 'check_terms',
     'label' => 'Terms of service',
     'rules' => 'callback_check_terms'
)

A very simple function in my controller below just checks the input and provides a custom error message

Code:

public function check_terms($terms=0){
     if ($terms != 'agree')
     {
          $this->form_validation->set_message('check_terms', 'The terms of service must be read and agreed to before continuing.');
          return FALSE;
     }
     else
     {
          return TRUE;
     }
}

I wanted to make the function above 'private' so it couldn't be accessed by the URI but obviously this prevents the helper from accessing the function. I cant add the underscore to the function name because the callback doesn't seem to accept it. I was thinking of using the _remap function to send 'check_terms' in the uri to the 404 but this seems a little overkill.

Can anyone suggest a more elegant solution?