//protected/components/helpers/SpellHelper.php

class SpellHelper {
    public static function spell($number){
        //implement function put to $result
        return $result;
    }
}
//protected/components/behaviors/SpellBehavior.php
class SpellBehavior {
    public function spell($attribute){
        $model = $this->owner;
        $val = $model->getAttribute($attribute);
        if (isset($val) && is_int($val))
            return SpellHelper($val);
        else
            return NULL;
    }
}

class Model extends CModel {
    public function behaviors(){
        return array(
            'behavior' => 'SpellBehavior',
        );
    }
}