Well, you'd have to use FTP functions to do it. If no one else helps by tomorrow I'll see if I can type the code up.
Why wouldn't this be in a database anyway?
[EDIT]
You want it to look like this...
<textarea>
<?php include 'banned.php'; ?>
</textarea>
or
echo ('<textarea>');
include 'banned.php';
echo ('</textarea>');