How to access the value of the editor?

Hi,

I want to build a simple preview within the page. So I replace the innerHTML-property of the content-div with the content of the textarea-element. Now I want to give my users the option to use FCKeditor. How do I access the current value of the editable area via Javascript? And how can I write it back to FCKeditor (at least FF uses only the value which was there when the page was loaded)?

Thanks a lot.