the elevator movement logic should be contained within the elevator actor, not within the widget. when the elevator creates the widget, it should pass itself as a reference into the widget. the widget should store that reference and use it to call functions in the elevator blueprint.
the elevator movement function can set CurrentFloorLocation, NextFloorLocation, and bMoveToNextFloor variables. then vinterpto on tick, if bMoveToNextFloor is true. bMoveToNextFloor would be set by a function called by the widget on click.