using this https://github.com/growthspark/wp-advanced-search I am not sure how to sort by meta_key value. I currently have a meta key called "Due Date" with the date entered like 06/06/2012 (M/D/Y). The search framework is nothing special, as it is simply php and wordpress codex standards so I hope someone can help.
I have something like this
$args['fields'] = array('type' => 'meta_key', label' => 'Test', 'meta_key' => '', 'format' => 'select', 'values' => array());
but it is not right. Any ideas?