I am using the code listed on the following link =:

http://www.magentocommerce.com/wiki/5_-_modules_and_development/catalog/programmatically_adding_attributes_and_attribute_sets

Everything works until the point:

    // Just add a default group.
    else
    {
        $this->logInfo("Creating default group [{$this->groupName}] for set.");

        $modelGroup = Mage::getModel('eav/entity_attribute_group');
        $modelGroup->setAttributeGroupName($this->groupName);
        $modelGroup->setAttributeSetId($id);

        // This is optional, and just a sorting index in the case of
        // multiple groups.
        // $modelGroup->setSortOrder(1);

        $model->setGroups(array($modelGroup));
    }

I am unsure where the object reference would need to be set from - I am attempting to have this as a separate file that can be automated - I am running this file by doing a

require_once 'app/Mage.php'; Mage::app();

Any help in this would be greatly appreciated

Thanks