Hiya Dazco, try the following.
Create an Adjustment Layer, contrast, curves, levels or whatever is appropriate for the repair.
Concentrate on the damaged area and adjust to correct that part.
Ignore the 'good' part of the area going off the scale
Click on the mask for the Adjustment Layer.
Create a gradient on the mask going from bottom to top and with the colours going from white to black.
This will hide the over adjusted 'good' part of the image, but allow the repaired area to blend into the image.
You may need to adjust the blend on the mask to get an acceptable blend, but give it a try.
I've used this technique often. Sometimes using it on a duplicate layer instead of just an adjustment layer.
This allows better control over the mask, opacity and blending.
Give it a try and post up your results.
(Post up samples of any future problems, it's easier to explain a real solution if we can see what the actual question refers to.)
Al.
