latest topics and extern.php

Hi-
I have been succesful with using extern.php and getting the lastest topics on a specific category to show on a HTML page. My question is how do show the Subject with some parts of the message (maybe 100 characters).

Do I need a mod or a plugin or is there a command that I can use with the extern.php file.

Thanks for any insight or help. Sorry if this has been asked before- I have searched for about 15 minutes to no avail.

-
Charles