Getting local call status and possible control of the call via DialPad desktop app

We're successfully integrated DialPad service in our CRM app (designed as WPF desktop app), calling DialPad desktop by custom protocol "dialpad://" plus parameters.

Now we wanna improve calling experience by implementing some features but I can't find a proper way. So, we don't have DialPad specific web service: just a two desktop apps; we don't have a plans to "expose" event subscription URL (and for the God sake, why we should? It's just a two local desktop applications)

Our goals are:

start DialPad call silently, on background and without actual ringing sounds (i.e. state "dialing"): show DialPad UI only if call connected and customer replied
if it's a voicemail prompt, hung-up with setting corresponding status

It's very simple to hide or minimize DialPad UI (I do have hWnd), or put our app window on the top, but I have no idea how to get local call status, any suggestions? Theoretically, I can control system volume: set "mute" during "dialing" and restore if call state changes. The only problem: how to get local call status?

Could you help me, please? Thanks!

P.S. I do understand: voicemail/autoreply detection isn't easy task and with 99.9% probability isn't implemented in DialPad.