hello NormK.
this might not be relevant to you but i too had a possum problem like that.
i purchased one of those high pitched non audible to humans squealer pest deterrents and put it inside my roof with an extension lead going down to beside my bed. whenever i heard a possum on the roof i would switch the thing on. I could here the possums eagerly trying to escape the noise.
as you have a dog this might not help.but it may just shut your dog up also.
