Flushleft and flushright in the same line (ConTeXt)

I have the following macro

\mainlanguage   [de]
\definepapersize[MyBook][A5]
\setuppapersize[MyBook][A5]

\definestartstop[Test][commands=\setups{Test}]
\def\Test{\doTest}
\def\Test[#1]{
\placeongrid[top]{
{\startalignment [flushleft] #1 \stopalignment \startalignment [flushright] (\bf Test Message) \stopalignment}
\blank[big]
}
}

\starttext
\Test[Wrong]
\Test[This one is correct, correct, correct, correct, correct.]
This one is wrong, wrong, wrong, wrong, wrong.
\startalignment [flushright]
(\bf Test Message)
\stopalignment

\stoptext


with three examples. What I want is this:

\Test[#1] should produce #1 and #2 with the following properties:

• #1 should be flushleft, #2 flushright
• #2 should never be breaked into two lines
• if they fit into one line, then they should do that, not like the above first example

How to do that?

-
What if #1 or #2 is larger than a line? What if #1 + #2 is larger than a line. If you ignore these cases then \hbox to \textwidth{#1 \hfill #2} should work. – Aditya Nov 1 '12 at 16:28
The only precondition is: #2 is smaller than a line. But #1 may be much larger, in any cases #1 should be flushleft and #2 should be flushright. And #2 should be in the last line of #1, if there is space for it. If not, then #2 has to be in the next line. – Mustafa Nov 2 '12 at 11:47
Are you trying to write attribution for quotes? Simply using \wordright{#2} should be sufficient. – Aditya Nov 2 '12 at 12:25
Indeed, that is it! – Mustafa Nov 2 '12 at 14:43

I am using the annotation module for a better key-value driven syntax (although you can also use \definestartstop). You can use \wordright{...} to place a word on the right. For example:

\usemodule[annotation]

\defineannotation
[Quote]
[
alternative=command,
spacebefore=big,
spaceafter=big,
command=\PlaceQuote,
]

\define[2]\PlaceQuote
{\startalignment[flushleft]
\placeannotationcontent
\stopalignment
\blank[samepage]
\wordright{\placeannotationtitle}}

\setuppapersize[A5]

\starttext

\input ward

\startQuote[title={Donald Knuth}]
\input knuth
\stopQuote

\input ward

\stoptext


gives

-