PBase

I hope I am posting in the right place.
I have a photo I need to extend the sides and top to a square sixe, from the usual rectangle sized photo. I need to extend the shading to the edge, keeping the same levels of gradient or shadow from the original. If I select the edge and transform it to the new canvas size it looks streaky. Does anyone know how to do this or understand my problem? I hope it makes some sense!

further to my last post, I thought I would includethe photo. I want to make a circular crop of the image keeping as much as possible, and moving her down a little. I will be very grateful for any tips you can offer.

http://www.pbase.com/truckle/image/47118788

The hardest part, as you probably know, is going to be the left side of the image. I had moderate luck selecting that area with the box tool (zero feather), creating another layer, then selecting the darkest and lightest colors and playing with the gradient tool until it looked close. It's not going to be perfect, at first, because the shadow isn't a perfect linear gradient. When you match the gradient moderately close to the shadow, you can use the clone tool and the band-aid tool to mix the the two together. After that, the top and right side should be a snap.

Chuck