kind of like this?
Okay, it might be hard for me to explain this so please bear with
First layer: background
second layer:
use the lasso tool to make a selection where the white line needs to be, on a new layer with the selection active, fill it with white, press the FX button at the bottom of the layers Palette, activat outer glow with these settings:

click okay, now set this layer's FILL to 0% bear with me
3rd layer:
right click on the second layer's icon, press select pixels, go to the background layer with the selection active copy it, and paste it in above the 2nd layer, desaturate it, and set the blending mode to linear Dodge.
4th layer:
duplicate the second layer and remove the effects from the duplicated layer, set it's fill to 15 percent
5th layer:
Duplicate the 4th layer, but set this one's fill back to 100% and set the blending mode to soft light.
Hope that made sense, i can always pass over a PSD