400 error message to be appeared

Hello, I try to make this error message appear though, I am not able to do it.
How can I set dynamic events to do it?

スクリーンショット 2019-10-11 09.24.22.png698×509 27.8 KB

スクリーンショット 2019-10-11 9.24.51.png3882×1790 577 KB

Thanks!