How to reset the Editor's Value via js

I have a one page ajax application that is reloading html page content in the background. This content needs to be edited in an existing fckeditor instance loaded when the page was initialized. How can I force the editor instance to set a new content in the editor after the editor was initialized (e.g .Create() was called). I tried simply resetting the fckeditor.Value field but it does not refresh the editor.

many thanks for any suggestions.