RMXP call event. How would you script it in?

The Common Events are located in the Database, and are events that are global to the entire game, regardless of what map you're on. These can be Called by the Call Event command.

If you wanted to call another event on the same map, make the "called" event 2 pages, and make the first page blank, the second page with a precondition of a Local Switch (since you're only affecting that map, may as well save a real switch for later). Also, Page 2 should be a Parallel Process.

When you want to start that event, turn on Local Switch A. When you want the event to end, turn off the switch..