public function afterCommitCallback()
    {
      parent::afterCommitCallback();
      if (!$this->getData('groups/tripletex_settings/fields/testmode/value')) {
     	  $api = Mage::getModel('tripletex/tripletex_api');
     	  $username = $this->getData('groups/tripletex_settings/fields/username/value');
     	  $password = $this->getData('groups/tripletex_settings/fields/password/value');

     	  if (!$api->setLogin($username,$password)) {
     	    Mage::throwException(Mage::helper('adminhtml')->__('Unable to login to Tripletex. Username or password for api is not correct.'));
     	  }
      }

      return $this;
    }