Using "Spare" Button on Steering Wheel E Class

Anyone know how to access the wiring for the "Spare"" button "Telephone Logo" on the steering wheel of E Class.

I like most people do not have a MB Cellphone fitted.

The toggle button should be capable of being used for something else -

E.G. One shot wiper, flash headlamp, clean headlamps. Etc. Etc.

If I could access the wiring to this the use of a latching relay or a momentary relay should allow a choice of uses for it.

Any have any info.

Mike Stone