Change background, check if open -- one file only ??

[William Case]

Hi;

I have been playing with this problem for hours.  Info-ed, wiki-ed and
googled; probably using he wrong search criteria. 

I have a notes.txt file I use to make extensive notes to myself while
working on a project.  I open it in a new frame so that it is next to my
'main' frame work and I can quickly cut and paste or write notes or
check previous notes.

I would like to add two features to this note.txt frame.  

Change the background (say colour linen) of this note.txt file when it
is open in this special frame only. The rest of the time the background
should remain standard white.

Secondly, I want emacs (.emacs) to prevent (or warn me about) two open
copies i.e buffers in any open frame, of this note.txt file when I start
to open this special frame.

-- 
Regards Bill