Trigger Relay When Door Station Pressed

Hello we need to momentarily close a relay when the door station intercom button is pressed to trigger paging. This is to alert night staff if they dont hear the master station. We can interface at the door station or hikvision DS-KM83012 master station providing we can momentarily close a relay when the intercom button is pressed

I am unsure how to trigger the relay by pressing the door station intercom button as opposed to using alarm inputs.