I want to use 2 different SIM cards in a Nokia N900 phone, and each one of the cards have different contacts stored. This is because one SIM card is mine, and the other is my brother's.

We need that, when starting the phone with one of the SIMs, the device uses its contacts, and doesn't store the data in the phone. By this way, changing the operating SIM no other contacts remain and only the current SIM are to be used.

This is my question:
How can we use directly the contacts in the SIM card without copying them to the phone application/data?