PeterNicholls,
What you are asking for isn't very clear. This is the forum for the MiVoice Office 250 not the MiVoice Business.
To put the MiVO-250 into Night Mode from a phone requires two things.
1. A phone set as Administrator. Go to System > Devices and Feature Codes > Phones > Ext XXXX > Flags > Administrator
2. The feature code for Night Mode. Go to System > Devices and Feature Codes > Feature Codes > Night Ring On/Off [Default: 9860]
Alternately, if the system is 6.0 or higher you could just log into the web page and put it into Night Mode there.
If you actually have a MiVoice Business MCD 3300 system then you would need to go to that forum and post a request.
Thanks,
TE