auto cross stave piano notes

[Rob Canning]

hello,

i have a string of notes for piano (one voice) spanning 5octaves that 
needs dividing between the two staves

is there a way to set a threshold pitch and say any pitch below that 
threshold will go to the bottom piano stave and anything above it will 
go to the top piano stave?

i can see how to do it manually on a note by note basis here:

http://lsr.dsi.unimi.it/LSR/Snippet?id=127

but i am imagining that this is something that can be automated, defined 
as \autocrossstave and turned on and off in a score as needed?

thanks

rob