Hello,
Here are your two best options. If css3 use http://css3pie.com/. If images you use 3 images 4 dives. Images are top, mid, bot.jpg. Top div holds top.jpg, mid holds mid.jpg with repeat-y, and bot div holds bot.jpg and nested in the the middle is content div which holds the padding. This is a fixed width rounded corner that will extend length wise as much as needed. If you need a flexible width box then you need about 8 images/divs.