Ok here is a little example i threw together. It basically gives you a keypad where you can enter a 4-digit key-code and check whether it is correct or not.

It is easily extendable to any digit-size key-code.

For your specific situation i would assign a pin-number to each keypad using the model's own skills or strings, and then when you press enter on the keypad, let my liitle example test against this key-code.

It is much easier to bring the panel up than to do it using the model. This is how games like splinter-cell did it, and it works.

Here is the example >>>
http://www.djbm.kawanda.net/public_files/keypad_example.zip