[NTG-context] another question about markings

Aaaand here's another question about markings: how could I compare the value of the top/bottom (or first/last) markings and have the header change accordingly? Example attached, it doesn't do what I (naively) expected it to do. All best Thomas \setuppapersize [A5] \definemarking[Head] \startsetups Headersetup \doifelse{\expanded{\getmarking[Head][top]}}{\expanded{\getmarking[Head][bottom]}}{\getmarking[Head][top]}{\getmarking[Head][top] – \getmarking[Head][bottom]} \stopsetups \setupheadertexts[\texsetup{Headersetup}] \starttext \dorecurse{6}{\marking[Head]{Tufte}\input tufte\par} \dorecurse{6}{\marking[Head]{Knuth}\input knuth\par} \dorecurse{6}{\marking[Head]{Tufte}\input tufte\par} \stoptext