add variable from custom field in shipping e-mail

-- url of the page with the problem -- : www.hiphey.be
-- HikaShop version -- : 2.6.3
-- Joomla version -- : 3.5

Hello,

I would like your help again.
I have created a custom field in the back-end where the admin can enter a tracking number.

I can get the tracking number to show itself on the e-mail by using {VAR:order.tracking}

Now i want it to be in a clickable link. The code to display it on the e-mail works.
But i wanted to add the link to the post company so that the customer only would have to click the link to see the tracking info directly.

I have been able to show the link itself using this code in the preload part:

$url_Tracking = $data->order_tracking ->$data->cart->order_tracking;
if(!empty($customer->user_cms_id) && (int)$customer->user_cms_id != 0) {
	$url_Tracking = '<a style= "color: #FFFFFF; " href="http://track.bpost.be/etr/light/performSearch.do?oss_language=NL&searchByItemCode=true&itemCodes='.$url_Tracking.'">Tracking code:'.$url_Tracking.'</a>';
}

'TRACKING_CODE' => JText::sprintf($url_Tracking),