Activate Humidifier via Zwave Thermostat and Relay

I have a Trane Thermostat and wanted to use it to control the humidifier instead of using the traditional sail switch / humidistat combination.
My idea was
Zwave plugin appliance controller → Transformer → Humidifier
Trane Thermostat → IF AC is on and in heat mode , toggle appliance
I’m looking at the Thermostat events and there are some when heat mode is set which I think is more when you switch the mode from auto to heat rather then when the AC is turned on in heat mode. Any suggestions on what event to use to do this?

Wow, we’re on the same wavelength for sure! I wrote some coding last night and posted on http://forum.micasaverde.com/index.php/topic,10508.0.html .