The only way that I have found to add a border to one side of a container is to add another object along the edge of the container to look like a border. If the display is stationary you can use a floating object to place it exactly. If the container needs to adjust in size you can place a text box formatted with the color you want inside the container and edit the width to create a narrow line on a side. So not exactly what you are looking for but hopefully this workaround helps.
Beat me to the answer, Kent.
I usually float another container behind the one I want abnormally formatted.
Actually, if you want borders on the sides of the target container but not on the top/bottom, (or on the top/bottom but not on the sides), and if you are going to get messed up by automatic sizing from device to device, you can consider stacking three containers inside of one floating container like I did in the attached.
superstore -- format sides.twbx 981.2 KB
Thanks All - I tried these workaround and they'll do just fine.