[SOLVED] Adding div to sidebar

I have an interesting design problem that requires adding another div tag to the sidebar. That div tag needs to contain all the widgets that the user adds to the site.

There may be another way to pull this off, but the only way I can figure this out is by adding a div tag (which I'm not sure how to). Here is a screenshot of the sidebar as designed in Photoshop:

The first rounded border can be applied as a background image, but the inner rounded stuff would require a separate div.

Any ideas on how to do this?