Joseph,
I think I followed what you were tying to do.. I would suggest creating a "floating" extension, and then using night service on the extension. Have the "floating" extension forward all calls to 402, and use night service on that extension to forward to 279. You would then have to setup the receptionist phone with "night service bell" so that she can activate and deactivate the night service at will with a star code.
Call flow:
Day
Incoming -- AA -- option 1 -- 450 (floating ext) -- Call Fwd all -- 402
Night
Incoming -- AA -- option 1 -- 450 (floating ext) -- Call Fwd night service -- 279
Thank you,
Darren