Ue4 i want know how to release the mouse after 【event on mouse leave】can do something

like this i drag something ,i want know what can i do after{event on mouse leave} , i can drag item until release mouse, spawnsomething(i know how to spawn). I JUST WANT TO KNOW HOW TO DETECT MOUSE RELEASE.
please help me ,感激不尽.

maybe you can try [event on drag cancelled],i just fool man.