resizable text section with a background with 4 curvy corners

[thosecars82]

Hello there
I would like to ask you this:I know how to make resizable butons with curvy corners using the sliding doors technique. But now, I would like to go one step further. I would like to have several different sections each of them having different backgrounds with curvy corners all fitting in the same page. As for the css layout, I do not have doubts to build the layout I want. But the problem comes because I do not know how to give a resizable background with curvy corners to each of these text sections which are resizable themselves. For example:
let's say I have a layout with 2 columns: right and left. And in each column I have 3 text sections one below each other. Now, I want to give each of these text sections a background which is different from the background on which these sections are laying. This background should have curvy corners and should be resizable just in case I wanted to add more text to any of this text sections.
I would appreciate any idea about it.
Thanks in advance