Originally Posted by jefro
Rescue mode is for times then your system won't boot.
That's one reason - the OP has another (equally valid) reason.
Must admit I'd go get another drive too - probably have one in my pile of "bits and pieces".
To answer the original question - no, you can't.
"linux rescue" in that context is a Redhat (CentOS) specific recovery environment. Grub loads it, but it has nothing to do with grub per se. Given that you managed a full CentOS install, I'd reckon you should be able to manage a rescue. Your call though.
Another option would be to dual boot another (possibly CentOS) system, and do your resizing from there. If CentOS, make sure you use different names for the LVM components so you can access them.
Won't help if your system is indeed unbootable from the hard-disk at any point.
A liveCD that has LVM and runs (completely) in RAM would also be an option - dsl/puppy/tinycore ... ? - haven't tried any in years.