Jean-Marc,
The event structure is fine. Since you are not using the timeout event, simply delete that case. I would also move the format string calculation inside the false case of the large case structure so that the calculation is only performed if a change is going to be made rather than every time the event occurs. It probably does not matter in this example, but it is generally good practice to avoid calculating things which are not actually needed.
On the Mac a degree symbol is typed as Option-Shift-8 = °
Lynn
