Arranging columns (rotated U-Shape). Do you know a way to do in ConTeXt (with or without column sets)?

[Leonard Siebeneicher <leonard7e@gmail.com>]

Dear readers.

Using ConTeXt MkIV.
I try to figure out how to use column sets such that one can place a 
column seperately beside other columns. I did not found a way.

The setup for columnsets should look like a rotated U-shape

%% /Page 1 _________________\
%% +------+ +------+ +------+
%% |      | |cset-1| |cset-1|
%% |cset-3| +------+ +------+
%% |      |
%% |      | +------+ +------+
%% |      | |cset-2| |cset-2|
%% +------+ +------+ +------+

Text should flow inside cset-1 columns automatically, without need to 
force column break by hand (like \column).

I get something like

%% /Page 1 _________________\
%%          +------+ +------+
%%          |cset-1| |cset-1|
%%          +------+ +------+
%%
%%          +------+ +------+
%%          |cset-2| |cset-2|
%%          +------+ +------+
%%
%% /Page 2 _________________\
%% +------+
%% |      |
%% |cset-3|
%% |      |
%% |      |
%% |      |
%% +------+

Is it possible to do with columnsets? Are there other ways without 
columnsets?

Thank you for reading.

Regards,

Leonard Siebeneicher

_____
My ConTeXt-File looks like

%% begin file
%% vvvvvvvvvv

\usemodule[visual]

\definecolumnset[cset-1][n=3,balance=yes]
\definecolumnset[cset-2][n=3,balance=yes]
\definecolumnset[cset-3][n=3,balance=yes] %% ???

\starttext\showgrid
\setupcolumnsetlines[cset-1][1][1][18]
\setupcolumnsetlines[cset-1][1][2][18]
\setupcolumnsetlines[cset-1][1][3][18]
\startcolumnset[cset-1]\dorecurse{2}{\column\fakewords{25}{50}}\stopcolumnset

\setupcolumnsetstart[cset-2][1][1][20]
\setupcolumnsetstart[cset-2][1][2][20]
\setupcolumnsetstart[cset-2][1][3][20]
\startcolumnset[cset-2]\dorecurse{2}{\column\fakewords{25}{50}}\stopcolumnset

%% Now lets return to line 1 on page 1 to overlap columns
\setupcolumnsetstart[cset-3][1][1][1]
\setupcolumnsetstart[cset-3][1][2][1]
\setupcolumnsetstart[cset-3][1][3][1]
\startcolumnset[cset-3]\dorecurse{2}{\fakewords{25}{50}}\stopcolumnset
\stoptext
%% Oops, a second page has been added

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