I wrote the above response before trying Craig's solution, which certainly does the business - thanks! Maybe this is one instance where a loop is the best solution. I'll leave it a while longer (no pun intended) before I implement it, to see whether anyone comes up with a set-based solution.
If you haven't even tried to resolve your issue, please don't expect the hard-working volunteers here to waste their time providing links to answers which you could easily have found yourself.