how to modify the grub.iso on UBCD ?

[xufux]

Hello,
i'm trying to modify the grub.iso on ultimate boot CD (using Winimage for instance)
i'd like to add my own entries in the menu.lst but when i update menu.lst on the grub.iso image, the grub menu don't load, i just have the grub prompt.

i've been on http://mirror.aarnet.edu.au/debian/pool/main/g/grub/
but i don't now what to do with these files to build my own version of grub.iso