how do i set up the remote to work with multiple recievers of the same type?

Alas you can't, unless the receivers themselves have provisions for it. Both will respond as one. You *could* experiment with X-10 switches to power one or the other on, maybe an IR routing function, but it may costing more in products and time than to simply buy a different receiver. :-)

I have the same problem, one receiver is for the home theater, and the other older (same model) is for the rest of the house. I simply put black tape over the older receiver's eye and just get up to turn it on whenever I need it. Obviously a very inelegant solution, but I could not pass up the deal on the new receiver!

Daniel is correct, but if you would like to check out some very cool ir devices ie. relays, routers etc., check out a company called Xantech, they have reasonably affordable ir routers.
Another tip:
you can use an ir repeater system for both units, making sure you block both ir windows. what you can do is use a radio shack catv remote a/b switch to interrupt the signal to one or the other. pretty cheap alternative, i havent actually tried it yet, but it should work. let me know...

SORRY
USE THE RCA IR VID SWITCH TO GATE THE SIGNALS

Just did a media room for a customer with 3 DTC-100's, used an ir router from Xantech and it works flawlessly. You can control all three, just two or each one sepaerately.