Trigger event via key?

[rotodisco]

I want the player to bring a key and put it in a certain spot, which triggers an event. I don't want to end the level or change section, just trigger an event. I could put a zelda 2 key door in the floor, so that you can put the key on top of it, deleting it and allowing a koopa to kick a shell at a block which triggers an event...but this leaves a hole in the floor, i have to change the door sprite so i can hide the koopa far below, and you'd hear the shell kicking sound constantly until the key is used. I can't really get around this via level design because what I'm doing with that room is set in stone. I thought the keyhole would be able to trigger events, but it's just a level exit, right? Is there a way to do this using Luna or something?
I'm using PGE/Horikawa's smbx 2.0.

I'm respriting it anyway, so it doesn't have to be a key- it could be a friendly, nonmoving shyguy or a mushroom block or something.

[bossedit8]

You can make the key with the event "death" on it and then it can trigger it as soon as you enter the locked warp position in a level. If that's what you mean.

[Valtteri]

I don't understand why you would need a Koopa. You can just set an event to happen when the Zelda lock dies. Every NPC can trigger an event upon death and the Zelda lock is no exception.

[rotodisco]

I don't understand why you would need a Koopa. You can just set an event to happen when the Zelda lock dies. Every NPC can trigger an event upon death and the Zelda lock is no exception.

because i'm a dumbo who overcomplicates things. thanks!