314754 Extend a Photoshop Image

I have a background image I inherited that is 700px in width and it has some gray places on it to create a faux column and border shading. I've attached the image so you can see it. I don't want the height to change. I don't want the width of the gray areas to change, but I want the white space between the left gray block and the right faux column to be extended, so the image itself stretches out to 850px. I also want the image to remain a .jpg; no .pngs or .gifs, please. Payment will be sent via PayPal only, and payment won't be made until I can test the image out in the site I'm building. I need this done, like, yesterday.