Editor window and image with relative path

Hi,

I want Fckeditor to show an image wich is not in the fckeditor directory :
_root
|_js
|_fckeditor
|_img
index.php

to show an image i use 'index.php?img=newImg.gif'

if i insert an image in fckeditor with this src, i can't see my image, whereas if i validate the contents the image is ok.
Is there any way that would force FckEditor to consider _root as the image directory ?
I don't want to use absolute path, i really want to record the img tag with the relative path.

Thanks