KickStart postscript problem

Hello everyone:

Im not going to explain about kickstart, i supposed you know, that one of the features of this program is to run a postscript after installation.So after install packages you can run a set of commands to make a "first-configuration" of your system.
Usually people writes all the "postscript-commands" in the kickstart file like we would do in other scripts. But i want to run this commands from a different script apart of kickstart file.
So i have a file in "ris-server" called postscript.sh and i want to run it in kickstart-client machine just before installation. How to do it ?!?

I have tried mounting the directory of "postscript.sh" and copy to client-machine and run it ; i have tried copying directly, and several ways, it never works....

Like:

%pre.....
.
.

%post
mkdir /tmp/ris
mount "ris-server-ip":/tmp/ris/postscript.sh /tmp/ris
source /tmp/ris/postscript.sh #This run all script

%packages.....
.
.

It never works some idea plz ?!?

Thxx