Ahh ok gotcha. No that wont work. Your character walks into the trigger. Your Character is not a door so cast will fail naturally. For this to work your door has to walk into the trigger or the trigger into the door (I assumed the overlap was on your character). Basicly you never get a door refference the way you got it right now.
But fear not you can add a DoorBP variable, make it editable, select it in the Scene and set the refference to the door you want to trigger. On your Begin overlap get that variable and hook it into Door Lift Event. No cast needed unless you want it to limit to the player only as example.
Thats it.