Handlers for entities?

I'm using expat in an XML editor I'm writing.  So far, it has been  
perfect.  Now I need to have a handler called for entities.   For  
example, if I have a document like this:

<?xml version="1.0"?>
<chapter>
   <title>Advanced Topics</title>
   <para>If you want to go skiing &mdash; I suspect you do &mdash;  
get on the bus.</para>
</chapter>

At the moment, expat chokes on the &mdash; and fails to parse  
("undefined entity").  I'd really want it to call one of my functions  
so that I can deal with the entity in my code.  Is this possible?

Thanks in advance,
Aaron Hillegass
Big Nerd Ranch, Inc.
http://www.bignerdranch.com/