C# KeyBinding when application on background

Question

Possible Duplicate:
How can I register a global hot key to say CTRL+SHIFT+(LETTER) using WPF and .NET 3.5?

I want to create a shortcut for my WPF application.

The application should be invisible most of the time and when Ctrl+N is pressed application should appear. I tried to do this like that :

Mcommand m = new Mcommand();
KeyBinding b = new KeyBinding()
{
  Command = m,
  Modifiers = ModifierKeys.Control,
  Key = Key.Q
 };

m executes when an application is visible. But when application is invisible it doesn't works. Any idea ? Thank you.