Perhaps you can have more help here http://discuss.ardupilot.org/c/ground-control-software/mission-planner where you can find the MP developer.
I agree, you need to talk to the Mission Planner developer, Michael Oborne.
At the forum link Cala gave you above, he is the blue "M" and your best bet would be to ask this question on that forum.
Mostly all the Ardupilot stuff is now over at the Ardupilot site now, not here on DIYDrones any more.
Change your keyboard on the bottom box right of your screen(left click(Mine says ENG)) to the proper language, here in canada ours flips to french lol!!!
Might work for you....