The unlock code is held by motorola and cannot be generated via a program like some Nokias, you can buy this code from various online companies who pay to access the Motorola server, or direct from the service provider.
a different way is to get it unlocked in an independent phone shop or a market stall.
the old version of the V3 could be unlocked at home with unlocking software and the USB lead but the recent version needs "testpoint" unlocking where a contact needs shorting within the phone while running the unlocking software.
http://www.youtube.com/watch?v=1zkmZSHc8bs