You need to use switches and when setting up an event there are 5 options...
Action Button
Hero Touch
Collision
Autorun
Parallel Process
Okay, now set to hero touch so when they touch the square it activates. Collision when you want the person to walk into the event and it suddenly happens... Autorun and Parralel Process for it to start instantly. They work different in some way, no tsure yet.
Also I've never had a bug with being able to move during an event.. unless it's say like "Play BGM".