// Who is sending the IM
$pmfrom = array(
	'id' => $ID_MEMBER,
	'name' => $context['user']['name'],
	'username' => $context['user']['username']
);

// Who is receiving the IM		
$pmto = array(
	'to' => array($row['ownerid']),
	'bcc' => array()
);
// The message subject
$subject = sprintf($txt['shop_im_trade_subject'], $row['name']);
// The actual message
$message = sprintf($txt['shop_im_trade_message'], $ID_MEMBER, $context['user']['name'], $row['name'], formatMoney($row['tradecost']));
// Send the PM
sendpm($pmto, $subject, $message, 0, $pmfrom);