Event click outside window (my project). (Edited)

I want to get event "Click outside Window"When click mouse any where, my window still get the event.

Ex: 

i have
----------------------------------------
int i = 0;

public void clickOutsideApp(........., ...........)
{
        //code...........
         //click on the destop or any where outside of my App => 

 i++; 
        textview.Text = i.toString();     
}
----------------------------------------
Run:
http://i1120.photobucket.com/albums/l486/hjkromeo/1.jpg

When i click on destop:
http://i1120.photobucket.com/albums/l486/hjkromeo/2.png

When i click on my computer:
http://i1120.photobucket.com/albums/l486/hjkromeo/3.png
----------------------------------------
I'm sorry, my English is so bad.

Please help me. Thanks!