I guess a can of compressed air could help, though it's hard to say how well it would work against the powder-like sand in Iraq. I haven't been there but my cousin and one of my friends have both been deployed there at various times and they tell me the sand is much finer than it is in the U.S. and it gets EVERYWHERE. Compressed air cans are generally meant for dust, not sand, but it might help anyway.
I remember seeing a picture of a journalist who was using a PowerBook G4 12" outside, but he was using it through what looked like a glorified plastic bag. I wouldn't run it for long periods of time inside a plastic bag though. The biggest thing is to prevent the sand from getting inside in the first place, so making sure you only use it when you're inside and away from open windows/doors.
Another couple things you could do would be to see if you can get a screen protector and/or a keyboard protector for it. Not sure if that stuff is available out there but I've seen rubber keyboard shields that fit over keyboards and prevent stuff from getting in between the keys. A thin film screen protector might also be nice to prevent any sand that gets inside when the lid is closed from scratching the screen itself.
Good luck, I appreciate what you're doing for our country!