How to use script when chainloading from UEFI GRUB

[dthatcher]

Greetings,

I have a UEFI bootable USB stick which I want to use to load iPXE and run a custom script.
Here is the GRUB2 entry:

menuentry "iPXE"{
search --no-floppy --set=root -f /live/ipxe.efi
chainloader /live/ipxe.efi + 1
}

I have placed a plain text file script at /live/script.ipxe but it doesn't see the script. What do I have to do?

Thanks,
David