Animation Region Render

[DMerz III]

I could be totally ignorant, but does anyone know if it's impossible to region render animations?
Been using animation more and more lately, and would love to patch certain parts in without rendering the entirety of each frame in order to save some time.

I'm sure there are coding issues with this, but it is definitely a wish list item for me. Apologies if it has already been mentioned somewhere, I did a forum search and didn't come up with a result.

Thanks,
David Merz