[NOT ISPCP RELATED] ProxyPass to old server in a lan

[lukeduck]

Hi,
I would like to install one new server (Debian+Ispcp) behind the firewall router, and use ProxyPass Directives in to redirect old sites on the old server in the lan for testing.

Here is an example of the directive i want to put in ispcp :

<VirtualHost *:80>
ProxyPreserveHost On
ServerName modele.francejoomla.net
ProxyPass / http://ip.old-server/
ProxyPassReverse / http://ip.old-server/
</VirtualHost>

My question is :

What is the process in ispcp ?

Where to put this directive ?

Luke