extending validation

[eluser]dimis[/eluser]
I put at MY_Validation

Code:

function _check_setbox($val) {

       if ( $val !='-1') {
           return TRUE;
       }
else
   {  $this->_error_messages('_check_setbox', 'You must select a value.');
      return FALSE;}

I call it as

Code:

$rules['material']    = "required|_check_setbox($material_id)";
$rules['type']    = "required|_check_setbox($type)";
$rules['collection']    = "required|_check_setbox($collection)";
$fields['collection']= "collection";
$fields['type']= "type";
$fields['material']= "material";

But it does not work