How to get acces to HMD events when stereo rendering is turned off?

I’m trying to get switch VR/NonVR mode only by put on or remove HMD from head, but after switching stereo to OFF there is no access to any HMD event enable anymore.
I was trying ti use “Enable HMD” node and vr.bEnableHMD consol command after switching stereo to off, but no result.
Is there any way to trace HMD events when stereo rendering is turned off?