Marilyn,
A much better way to dodge or burn is to add a new layer, change the blend mode to "soft light" and fill with 50% grey (just check the box). You can then dodge or burn by using a paintbrush and selecting black or white as foreground color, plus you can not only adjust the opacity of the brush, but the entire layer as well.
Hope this helps,
Fred
www.fredgibbons.com
