NZDUSD synthetic cross

Basically, make yourself a "synthetic cross" called NZDJPY. It's no different than the true NZDJPY cross, except Oanda doesn't offer NZDJPY. (Some brokers do).

The price of your synthetic NZDJPY at any given time is just the product of NZDUSD and USDJPY.
For example, if NZDUSD is at .6931/.6936 and USDJPY is at 105.66/105.69, then NZDJPY is at 73.23/73.31.

Now, you want to buy NZDJPY on the dips in its (synthetic) price. Great. Here's the recipe:

Buy X units of NZDUSD and simultaneously buy
X * NZDUSD price units of USDJPY. Why? Because when you buy X units of NZDUSD, you are long X units of NZD, and short X * NZDUSD price units of USD. To cancel out the short USD, you go long that number of USD.

Example:

Buy 100K units of NZDUSD at .6936
Buy 69310 units of USDJPY

Look at your exposure tab. USD exposure should be very close to 0. NZD is long, JPY is short.
Now you will collect about $8 a day on your NZDUSD position and $3 a day on your USDJPY position. And you will have no exposure to the volatile US dollar.



Source:
Oanda Fourm Discussion

Additional Reference:
http://www.currencysecrets.com/2006/07/27/synthetic-positions/