lcd projector + elmo in a bright room

aloha and sorry if this is not the right forum for my question.
I want to use an elmo aqnd lcd projector to display student math and written work, textbook pages, typewritten text, laptop output and whatever else comes up onto a whiteboard in a room with windows on two walls.
Rigging drapes isn't gonna cut it, but we have watched a movie on an lcd projector playing from my laptop and that seemed okay.
My question is, what specs do I need to look for in a projector and is there any hope for getting one that fits those specs for less than $400?

Mahalo,
Mike

Don't quite understand. You have a projector that works, but you want to buy another (cheaper?) unit?

Edit: For a room with significant light you need a projector with high brightness. The other consideration is the resolution. Higher resolution is better, but also costs more. Here are some reviews of popular projectors of various resolutions for the classroom.

sorry for the confusion. our school has two projectors and two elmos for k-12 , so it's a limited use situation and I would like to have unlimited use. I'm buying this gear with my own money, thus the tight budget. mahalo for the link.