Question about event dispatching inside a function

First of all i like to apologize for probably such a lame question but i am really new into UE4 and really cant find a point.

Here is the use case I have a widget blueprint that abstract several UI animations several functions like Init and Play. I like to attach an event dispatcher on animation finish but got

Create Event Signature Error: Unable to find the selected function/event: ‘CustomEvent_1’ - has it been deleted?

What is the workaround or at least best practice to dispatch events from BP Function ?