Variable within syslinux.cfg file

[steve.stamper at foremost.com]

I'm making my own boot & installation CD/ThumbDrive for RHEL5 - I'm having
fun doing some very cool things and all is going quite well.

I have multiple kickstart files on my NFS server and would like to be pass
a variable a the   boot:   prompt that can pickup and substituted in the
load string.  In this example, at the boot prompt I would like to enter
something like:

      boot:  custom ks61.cfg

in the syslinux.cfg file the kickstart "append" would pickup this variable
(using $1 for this example)

      ks=nfs:10.10.10.100:/RHEL5/$1

and the $1 would be substituted with ks61.cfg so the results would be

      ks=nfs:10.10.10.100:/RHEL5/ks61.cfg


Is this possible?  Any ideas where I can go looking & learning?

TIA - Steve