Use a field other than title in admin?

When creating a link to a custom post type the field to search on is the title. Is it possible to use a different field? I have a field called ‘billing code’ that I’d rather search on.

p2p_register_connection_type( array(
        'name' => 'must_be_billed_with',
        'from' => 'fee',
        'to' => 'fee',
        'reciprocal' => true,
        'title' => 'MUST be billed with',
        'fields' => array(
            'detail' => array(
                'title' => 'Details',
                'type' => 'textarea',
            ),
        )
    ) );

http://wordpress.org/plugins/posts-to-posts/