I want to do something like this
\marginnote{
\hspace{\stretch{1}}
\framebox{text}
\hspace{\stretch{1}}
}
i.e., center the marginnote. The problem seems to be that the width is defined to be that of \textwidth, so that the \stretch command assumes a margin width far larger than the actual 106pt. How can I redefine the width for \stretch?

\hspace{\stretch{1}}with\hss(TeX command for horizontal stretch and shrink). – Hendrik Vogt Jan 8 '11 at 21:27