How to use my own version of ArduPilot in Mission Planner?

Hi everyone!

I edited ArduCopter, in order to introduce a new MAVLink message. Now we want to simulate the drone in Mission Planner, using SITL. As our team understood it, Mission Planner’s SITL plugin downloads some external ArduPilot executable on the fly.

How can we use our own modified ArduPilot code instead?

Best Regards,
Peter

http://ardupilot.org/dev/docs/simulation-2.html#simulation

Update:
Hi Peter, thanks for the link, but we checked that out before, probably I should have written that in my initial post. We tried it with a linux VM on a Win host computer. on the linux vm sitl was running our customized ArduCopter code, while the win host was running MissionPlanner. Unfortunately there was some problem with the communication between vm and host. Perhaps the particular computer model used for the host has some issues with the used ports (driver problems or whatever).
So in the end we used an old Pixhawk, we had to run our ArduCopter code, instead of simulating it, and that worked.