\startsetups footer
    \getmarking[subject][first]\space-\space\getmarking[subject][last]
\stopsetups

\startsetups header
    \getmarking[section][first]\space-\space\getmarking[section][last]
\stopsetups

\setupfootertexts[\setups{footer}]
\setupheadertexts[\setups{header}]

\starttext

    \startsubject[title=One,marking=Whatever]
        \input knuth \par
    \stopsubject

    \subject{Two}
    \input knuth

    \subject{Three}
    \input knuth

    \subject{Four}
    \input knuth

\stoptext
