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

[abdobasha2004]

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>

but wher to put it to appear in rss?

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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);

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