No, you won't be able to do this. You can't have multiple phones work on one number simultaneously. Scott can probably go into a more technical explanation than I can, but the short answer is you only get one SIM per phone number.

Now, if you wanted to take your SIM out of one phone and put it in the other, then no problem - you can have as many phones as you like. The catch is that only one can be "active" with your SIM in it at any given time.

Hope this helps.

P.S. Congrats on migrating to Cingular orange while keeping your old blue calling plan. I'm waiting for them to offer this to regular retail customers.