Openlayers: Switching between 2 KML Layers


I am currently working on a map to display 2 kml layers switching based on a OSM Map as base layer.
Unfortunately my programiming competence is quite poor. Could you give me a hint how to
extend this script to get a switch for switching between 2 clicable kml layers?
One layer is working fine so far :

Many Thanks in advance.



the problem has been solved.
Here is the solution.

Regards Thomas