Sounds like you're away from the kitchen, so I wont make any food suggestions that would require a lot of work...
If you're looking to take in no calories when the hunger strikes, try some Trident sugarless gum... Also, I've been using a scoop and a half of Dymatize 12 hour with 30 ounces of water. Still tastes pretty good, and the volume of water is pretty filling.
Also - for work I've been packing Greek yogurt and chocolate whey in a small airtight container (requires a fridge)... Could also get by with a Clif Builder Bar in a pinch - or make your own protein bars if you have some time.
You should be eating something at 3:00, but I guess you're just worried about being so hungry that you'll pig out... My best suggestion (if you're back at the dorm or whatever) would be to have the big shake... then have a small bit of food after that.