I do not know if it's possible, but what i would like is a programmable button on the phones we use (grandstream 2000 and linksys spa921) to transfer all incoming calls to specified voicemail. At this time we just use voicemail with the opening and closing times. But lately it happens we are all on the road and nobody stays at the office to answer the phone. Direct calls to cellular isn't an option, cause if we are not in the office, we are in a meeting with a customer, and don't answer cells! So just a simple way to activate and deactivate voicemail.