Well no - you are right.
NeoGrub can't really be used to boot from CD (technically it can, but it's broken). But when you hide a Vista partition, the hiding persists until you use NeoGrub to boot into it.
So you can create a new entry, something like
Code:
title Prepare to Boot from CD
hide (hdx,y) # For all vista partitions
reboot
Then boot from CD once the reboot is over.