IP SIP Phone buttum setup


I read a lot abaut Asterisk pbx setup, but if you have for exsample a Snom 300 IP phone, and I like to program a key to turn PBX IVR to night setup ???
How ??
Perhaps someone can recomment some books for me.
I have read Asterisk the Future og Telephony, but I think I need a lot more detailed book.

Hope you give you time to answer me - Thanks.