Adding the sum of 2 pairs

[Forex Trader]

Is there anyone out there who has witten (or can write) an indicator that will add the price of two pairs together and plot the sum of the two prices as a line on the chart. I'd like to be able to add the sum of AUD/$ and CAD/$ and use it as an indicator. I promise I'm not lazy, I just don't know how to program MQ4.

George