First try;
$game_temp.common_event_id = id of the common event you want to call.
If that doesn't work try;
$game_map.common_events[id].interpreter = Interpreter.new
id = is the common event ID
You do have to edit Game_Map and Game_CommonEvent. Go to Game_Map and put this right under "class Game_Map"
attr_accessor :common_events
and then go to Game_CommonEvent and put this right under "class Game_CommonEvent"
attr_accessor :interpreter
I'm not sure if it would work, I didn't test it.