I have found my problem with getting no items. The Id in GetElementById should have been CE_<editor_id>_ID, where I was trying to access it with <editor_id>.

Now I have a new problem. The Item that is found it the entire dropdowntree and I would like to only get the the selected TreeItem. The DropDownTree consists of two levels (level one are groupheading and level two are the selectable items).

The example on http://cutesoft.net/example/JavaScript-TREE.aspx does nothing with the tree item. When I click the button nothing happens.