I'm having the same problem in that we're trying to allow text from a list box to be inserted into the html control.  Since we're selecting text out of the listbox the cuteeditor is losing focus.  When I use a simple textbox I can add an attribute (like onclick) to store off the editbox cursor so I can insert in the correct place after selecting.  I tried to do the same thing with the cuteeditor and the click doesn't occur in the document window, just the tool and page area of the cuteeditor. 
 
Could you provide an example of how to insert text from a second control (via doubleclick) into the cursor pos (which goes away during the doubleclick) of the cuteeditor?  Your example given works fine in that the button doesn't cause the editor to lose focus from what I could tell...
 
Thanks!