Multiple is_unique and set_message

[eluser]Noobigniter[/eluser]
Yes, for a field it works fine, but I want different message for each, like this example:

Code:

$this->form_validation->set_rules('page', 'Page', '... |is_unique|xss_clean');
$this->form_validation->set_message('is_unique', 'Cette %s est déjà présente, blabla blabla blabla');  

$this->form_validation->set_rules('otherfield', 'Otherfield', ' ... |is_unique|xss_clean');
$this->form_validation->set_message('is_unique', 'Ce %s est déjà présent, huh huuh huh huuh huh');

I thought it was possible to do directly, but if this is not the case, I would call the callback