this worked some time ago. Current minimal mkiv \def\tabulateuse#1{% \dorecurse{\numexpr2*#1-1\relax} {\span\omit}} \appendtoks \let\use\tabulateuse \defineTABLEshorthands \to \everytabulate \starttext \starttabulate[|l|Bc|c|c|c|r|] \NC a\NC b\NC c \NC d\NC e\NC f\NC\NR \NC a\NC \use2 b\NC d\NC e\NC f\NC\NR \NC a\NC \use3 b \NC e\NC f\NC\NR \NC \use4 a \NC e\NC f\NC\NR \stoptabulate \stoptext system > tex > error on line 10 in file 09-02-30.ctxcrop: Undefined control sequence ... 1 \def\tabulateuse#1{% 2 \dorecurse{\numexpr2*#1-1\relax} 3 {\span\omit}} 4 \appendtoks 5 \let\use\tabulateuse 6 \defineTABLEshorthands 7 \to \everytabulate 8 \starttext 9 \starttabulate[|l|Bc|c|c|c|r|] 10 >> \NC a\NC b\NC c \NC d\NC e\NC f\NC\NR 11 \NC a\NC \use2 b\NC d\NC e\NC f\NC\NR 12 \NC a\NC \use3 b \NC e\NC f\NC\NR 13 \NC \use4 a \NC e\NC f\NC\NR 14 \stoptabulate 15 \stoptext Herbert