Dodge tool, right click on the burn tool, looks like a lolipop

--
f=Ma well, nearly...

Use your marquee tool Select the area you want to adjust. Set your
feathering to an amount that blends the adjustment, (you'll have to
experiment with this. Now, make your adjustment.

Another approach would be to copy the image to a new layer then make your
adjustment to the background layer, now with your eraser tool set to about
a 50% opacity you can brush in the adjustment.

A third way is to do a levels or curves layer mask.....

If you need more detail, just let me know...

Pat Ziegler
www.imagequest.netfirms.com