Help with adding an event trigger to a block

[Adenharry5]

How can I make it so that when I place a specific block, it’ll trigger a game event to spawn zombies? I already understand the gameevents part of it and am more so wondering how I can add this trigger to the block, as I’d assume this done with some sort of property within the blocks.xml file. For context, I’m working on a supply drop mod where, once you place the signal for it, a supply drop will drop at that location. I already have this completed, but I wanted to make it so that after you place the signal, you’ll have to fight zombies while waiting for the supply drop to come. Any help is appreciated. 🙂