There will be many ways of doing it - depending on how things are set up. The below assumes there is only 1 Wall and it is in the level already, and so are the Coins.
make the wall disappear after collecting a certain amount of coins
- in the wall actor:
Whenever a coin gets Destroyed, the Wall adds 1 to the counter. When we hit the threshold of 5, the wall destroys itself. Would that work for you? Do tell as there are more ways, some better than others.
One note:
Avoid calling stuff after Destroy (self), chances are this actor is gone and there is no absolute guarantee the following nodes will be called correctly.