Okay, what you need to do is to use "self-switches". Get rid of the erase event command (or whatever other command you used to make the person disappear), and replace it with the "Control Self-Switch" command.
Turn on whatever switch you want to use for your event.
Once that's set, go up to the top and click "New Event Page".
This will create a second, blank page. As long as it's blank and not set to Autorun, it won't do anything. All you have to do now is to set the conditions on that page so that it won't run unless the self-switch you assigned is on.
And it's as simple as that.