Can I update my in car CD to include sat nav?

I have just aquired a 2004 Nissan Almera Tino with the usual fitted Nissan entertainment system comprising radio, cd as well as environmental features and vehicle info/history. I have noticed a button embossed with the word MAP. When pressed this does absolutely nothing, can I purchase a software update for satnav prposes or does this have either a completely different function or indeed no function at all?