Create refocus effect for a image? I have got this image:

The idea is seperate the image to two using mask in U/V image editor, then blur each one to make it look like the camera changes its focus from the man to the ipod:


I've got the mask. But how I do that in node editor?

Blend file:
Ok I got it here. It's hard to do this in only blender. Using photoshop would simplify this..
    The idea is simple. Open photoshop (or GIMP whatever..) => load the image in => Cut it into two (Each one has a focal point, near and further) => Export them as PNG => Load the two images into Blender => Composite them, blur each one at a time to fake this defocusing effect!