Does annybody knows an easy way to set environment variable when I can't save changes into hard disk?

I start linux from live-CD of LFS, so I can't save changes when modifing

an evironment variable. Now I know I can use command 'export' to modify an

environment variable from shell, but I can't write it into a script file, and I

must type such commands a lot of times to set all of my environment variables when I reboot my computer.
(When I run the script containing command 'export PATH=/bin', the environment

variable PATH will not be set appropriately)
thanks

I find the answer now, I write a script file like this:

export LFS=/mnt/lfs
ln -s $LFS/tools/ /tools
export PATH=/tools/bin:/bin:/usr/bin

and use command 'source' to run the script file.

I remember reading someplace, maybe on the Livecd site, somebody had some scripts for running when you leave and come back.

Maybe it was in the hints section.

thank you very much