multiple editor's tag in a xul window

Hi:
   I was looking for a way to embed multiple editor tags in a xul
window. Actualy, if you try, only the first one seems to be working, do
not matter if you encloses it neither in a iframe nor in a xbl tag  nor
in a iframe inside a xbl (I had tried too....). Then, how can I start
to develop this feature in the mozilla code? any hint? Do I need to
fill a bug?
   I would like to develop it, but, there is no much documentation as
far as I have been looking for it.
   Thanks in advance. Mariano.