edit /boot/grub/menu.lst
add the following with correct partition.
# for QNX Neutrino
title QNX Neutrino
root (hd0,3)
savedefault
makeactive
chainloader +1
To get partition details run fdisk -l command
hd0 specifies hard disk and 3 specifies Qnx partition. (Install Qnx boot loader on its partition. Not on the MBR)