Для правой кнопки мышки СКОРЕЕ ВСЕГО даже через API нельзя повесить событие.
Вот выдержка из документации класса MPxContext:
Since there are default actions for all tools in Maya, such as the right mouse button event which brings up an options menu, only as subset of the events that occur in a view can be overridden.
The events that can be overridden are:
doPress - mouse button press event (left & middle only)
doRelease - mouse buttons release event (left & middle only)
....
А вот выдержка из документации класса MEvent:
Since Maya has default actions for several events, only a subset are avalaible through the API.
The events that can be accessed are:
buttonPress - mouse button press event (left & middle only)
buttonRelease - mouse buttons release event (left & middle only)
....