Populating RSForm dropdown box with PHP

[Acrocephalus]

Hello,
I'm trying to populate a dropdown box in a RSForm using this code:

//<code>
$db = JFactory::getDbo();
$db->setQuery("SELECT Bruel_ID FROM mpctz_rsform_bruels");
return $db->loadObjectList();
//</code>

However, it displays nothing in the box and some code outside of it (see attached file). Can anyone help?
Thanks,

Dani