Please see this extract from our page on Banking, Money and Taxes in Norway:
Expats planning to stay in Norway for more than six months, will have to register at the National Population Register (Folkeregister) in order to apply for an 11 digit national ID number which consists of the holder’s date of birth, and a five digit personal code. Applicants will require their passport and residence permit. They will also have to fill in the form titled “Notification to the National Registry (NR) of move to Norway from abroad”.
If someone is not yet a resident, they can receive a temporary number at Skatteetaten, the Norwegian Tax Authority. A D-number (dummy number) is a registration number for foreigners who are not yet registered in the Norwegian Population Register.
It seems to me that the best course of action for you will be to apply for a temporary number with the Norwegian Tax Authority. You should get in touch with them directly to find out the exact process.