page breaks before titles

[mf <massifr@fastwebnet.it>]

Hello,
I'm trying to typeset a book made of letters with ConTeXt.
Every letter has a title a subtitle and a date, before it
starts with "Dear ..."
Like this:
---------------------------------
          Title
         subtitle
                    where, when
Dear ...,
the rest of the letter
...                 
---------------------------------

The letters are very different in length -- some are long,
some are made of a couple of lines --, so I'd like to
typeset them continuously, without skipping to a new page
every new letter (\setuphead[LetterTitle][page=no]).

This way a letter could finish beyond the half of a page,
and the next one could have no space left to get the part
from Title to the first lines of the body on the same page.

That's why I disabled page breaks from Title to the first
paragraph after "Dear ...": it would be ugly having only
the title in one page and the rest in the next ones.

But there's a side effect: the title of the new letter
"pulls" the last two lines (the penalties are set to avoid
one-line widows) of the previous letter to the new page,
even when there's room for them on the previous page.
In this case I would like ConTeXt to break the page at
the end of the previous letter, before the next letter title.
That's why I've set 
  before={\blank[2*line]\page[preference]} 
in LetterTitle. But it does not work.
Example:
         ---------------------       ---------------------
         text of the previous        text of the previous 
         letter with room to be      letter with room to be
         all typeset here            all typeset here
page 11                              last two lines of the
         [room for >2 lines]         the previous letter

page break-------------------   ==>  -------------------
         last two lines of the             Title
         the previous letter             subtitle
                                     ...
page 12       Title
            subtitle 
         ...

         --------------------        --------------------

Is there a way to know the vertical location where the
previous letter ends, to decide whether to skip to a new
page?

Thanks in advance,
Massi



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