Nevermind I can't do that even if I WANTED to because NO BODY trades bitcoin in NZD on MtGox.
Don't worry about trading BTC for NZD on MtGox. The order books are connected at +/- 2.5%. When you sell to a bid, the bid can be in any currency.
You can even sell BTC for NZD to yourself and buy the same BTC in USD. It is a form of converting currencies and taking the hit of the spread. I did this converting some JPY to USD some time ago; it was a mistake by me but it worked.