Force Read more ... link to appear in RSS exporter

I want to force a link to the thread to appear in the first part or any part if used / grabbed in RSS aggregator
any ideas
simply i think the link will be like :

<a href="showthread.php?$session[sessionurl]t=$threadid">Read more ...</a>

HTML:

but wher to put it to appear in rss?
here is a piece of code in external.php:

$postbit_obj =& $postbit_factory->fetch_postbit('external');
						$message = $postbit_obj->construct_postbit($thread);
						$xml->add_tag('content:encoded', $message);
						unset($message);

PHP:

so i need $message to be a link for the thread for example or added link read more after it

 

please any body help
I am being copied a lot !