Can I use an apt-cacher to install?

[David Goodenough <david.goodenough@btconnect.com>]

I have a server which runs apt-cacher.  I use it for all apt-get updates and 
upgrades on my system, but I have had no luck trying to install using it.

I tried setting it as the proxy (i.e. using the insertion of the proxy bit
at the start of the URL to gain access to the server), but that did not seem
to work.

Is there a way of taking an existing Debian mirror address from the list
and then modifying it, so that I can add 10.0.1.1/apt-cacher to the front
of it?  Or do I have to enter the entire mirror address including the bit
above and if so how do I say to the installer that I will enter the address
rather than taking one from the list?

Thanks in advance

David