minimumVerticalExtent override?

[Doug Asherman]

Hello, all:

I know that you can globally set the space between staves in a 
StaffGroup by setting minimumVerticalExtent in a Staff context.

However, I'm looking for some way to temporarily override 
minimumVerticalExtent _after_ having set it globally in the \score 
block. Something like "\override Staff #'min-vertical-extent, etc."

Honestly, I've read the manual and can't seem to find how this would 
work -- though I believe I've seen it done.

I'd really appreciate it if anyone could point me in the right direction.

Thanks,

Doug