Unlike pan functionality, "width" isn't a standard control that you'll find in most DAWs. Usually, "width" processing is done using M/S, delay, or phase-based processing. If you hunt around you should be able to find some plug-ins that perform this function.
My personal favorite stereo-imaging processor is
Dr. MS, which uses M/S processing to create stereo width. There are TONS of plugs out there that will perform similar types of processing though.