Doing it now..... problem is that as random as it is there is no way to really know if it worked.....it could be hours before it does it again....lol, damn technology.
I have an app called Quick Profiles on my Droid. Perhaps you can give it a try... I have some profiles set up on my Droid (Normal, Night) and you can specify settings for the notifications and ringers. I have only my phone ringer active on the Night profile, all other notifications are off.