mac address in install.cfg

[jad at nominet.org.uk]

Hi,

I am doing network installs of FreeBSD 6.0 and I want to place the install 
files in a directory that depends on the mac address of the server being 
installed. In install.cfg I want to specify something like

nfs=10.0.0.1:/var/net_install/files/$MAC_ADDRESS
mediaSetNFS
package=db42-4.2.52_4
packageAdd

Where the target server substitutes $MAC_ADDRESS at install time. Can 
anyone think of a way of doing this?

Thanks
John