Automating a letter module style

[Nigel King <king@dircon.co.uk>]

I have been using a letter format and gradually improving the macro format
and style each time I use it. It makes a lot of use of backgrounds to set
elements on the page. I would like to improve some other elements.
The target structure of a letter source would be as follows.
\usemodule[lett-01]
\setupletter
[address=...\\...\\..,
signature=Nigel King,
thedate=\currentdate,
......] 
\starttext
\opening
Further to your ...... %main letter content

\closing[Yours ...,]
\encl[...]
\cc[...]
\ps[...]
\stoptext

A lot of this works quite well using the following typical "macros" in
u-lett-01.tex typical parts of which are shown below
----------
\unprotect
\def\setupletter{%
  \dosingleargument\dosetupletter}
\def\dosetupletter[#1]{%
  \getparameters[letter@][#1]}
Some other \defs....
\def\opening{
\definelayer
  [letter@layer@toaddress]
\setlayer
  [letter@layer@toaddress]
  [x=\backspace,y=50mm]
  {\framed
    [height=37.6mm,
    width=89mm,
    frame=on,
    align={right,lohi},
    strut=no,
    offset=overlay]
    {\getvalue{letter@toaddress}}}
\setupbackgrounds
  [page]
  [background={letter@layer@toaddress}]
}% end of opening
\protect
-----------

The main problems that I have follow;
1. \usemodule[lett-01] has to be \input u-lett-01 because the definitions
are not recognized properly otherwise. "no macros found", I have not found
any documentation on macros. I had a look at m-chart.tex but it was too long
and complicated to get the simple idea from. Is there another
2. I cannot find a way of defining elements which are effectively in the
running text like \openingline=Dear ..., in the setupletter because
\getvalue{letter@opening} seems not to pick up the value. A similar problem
occurs with closing which has a number of formatting constraints which
deosn't want to be seen in the letter source. The only way I have been able
to achieve the objective has been to use the following type of construct.
In the source letter
\signature[Nigel King]
In the module
\def\signature[#1]{\def\fromsig{#1}}
\def\closing[#1]{\par\framed[width=\textwidth,frame=off]{\rbox{
  \blank[2*big] #1 \blank[6*big] \fromsig\par}}}

Any help would be much appreciated.
-- 
Nigel