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Do you have a bit more info on what your trying to do?
The easiest way to do this is have an event with 2 pages, first page is one that doesn't let you leave - like say an invisible event that moves the player backwards and have a text pop up like "I'm too young to die" when you touch it.
Then for page 2, you can have an event check for "Starter choice" under variables.
And just have it do nothing.