c++SimConnect - Toggle Autothrottle programatically without mapping input

Im trying to do the same thing but with “Recip Manifold pressure”, which is not in the Event_Ids. when setting a custom.event in the sdk examples, they never define which event they are trying to set. Would you know how I would declare which simVar I am trying to create a Cusom Event of? In my case, RECIP ENG MANIFOLD PRESSURE:1