My solution. Some hilarious misuse of tools but more flexible than the stock answer.
Half the fun of this is just going for this, solving it with 100 tools and then seeing the solution achieved in 3!
Before you can appreciate the elegant solution you have to live the pain of having a go.
Enjoying the experience emmensely.
(Didn't like the yzwz file type on the upload "content type (application/octet-stream) does not match its file extension and has been removed." Possibly because I'm on a much later version of designer? Anyway I zipped it.