WP8 - Hadndling the Home and Search Button

How to access the [[Home, Search and Phone Lock Button]] of wp8 in Unity via C#.

I want to call my GamePause() fuction, if user press the Home/Search Button.

I can access the Back Button via Input.GetKeyDown(KeyCode.Escape)
But I dont know how to access Search, PhoneLock and Home Button.

Thanks

u cant acces those buttons.
the home button will put the user to the home screen and search button will open bing.