How to run multiple application on mongrel using proxy?

hey im wondering how can i run multiple application on mongrel using
proxy. my supervisor wants it so that mongrel does everything for you.
for example mongrel should know that the relative url is
http://domain/myapp and he could change myapp to myappp2 to anything and
mongrel will know that automatically to goto http://domain/myapp2 or if
he was to remove the proxy mongrel should know that automatically.

i have no access to edit the proxy but all i know is that it looks
something like this

ProxyRequests Off
<Proxy *>
Order deny,allow
Allow from all

ProxyPass /myapp/ http://server:3000/
<Location /myapp>
ProxyPassReverse http://server:3000

also he is seriously against using the --prefix command on mongrol.
because you have to match the --prefix name to the proxy and wants that
to be more dynamic. is this possible?