Does someone know how to use the --CS switch of cgminer ?!

i can only use --CS 8 (for all blades) or only 1 blade (--CS 1, or --CS 2, ect ect)

i'de like to use 2 blade, and the other 2 blades on a different cgminer instance.
so u think --CS 1,2 would work... but i doesn't.

any help appreciated !