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and which part exactly doesn't let you do that? the most simple solutions are usually the best. set ev2 page to paralell, and conditions to switch[id]. after all the instructions in ev2 place switch[id] OFF. in the first event turn this switch ON anywhere you want.
Do a search in Game_Map for "passable?". Should have instructions on how to use it. If you also want to include events marked through, just copy the command. Rename it and get rid of the through check