Would like to trigger camera using Trainer button on DX4e

I’m still tinkering with my first quad build, which includes APM2.6 running Arducopter on a DJI F450 Frame. I am using a DX4e radio that came bundled with my PhoenixRC simulator. It’s billed as a 4 channel, but is really six. I’ve got different APM flight modes controlled by the CH5 switch, and I learned that the Bind/Trainer button comes through as CH6 (can see it working great in the radio calibration screen). I would like to use that button to output a logic 0 or logic 1 to control a small external camera I’m reusing. I’ve read dozens of posts online, reviewed the MP documentation, and tinkered quite a bit with the Mission Planner Camera Gimbal page, as well as the Full Parameter list, but haven’t been able to do more than get a PWM pass-through. I am after a simple 0/1 controlled via the trainer button on my radio.
Does anyone have any guidance on how to accomplish this with the gear I have?
Thanks in advance for any suggestions!