[NTG-context] max function in spreadsheettable

Dear all, I have a cell that calculates a value that may not be a negative value. If it is a negatiive value the cell should show zero. \startcell[style=normal] @ "0.2f EUR" $pauschale.eintag$ - ((D[row] * (0.2 * $pauschale.vororttag$)) + (E[row] * (0.4 * $pauschale.vororttag$)) + (F[row] * (0.4 * $pauschale.vororttag$))) \stopcell The $-variables will get resolved by Pandoc before ConTeXt comes into play. As far as I understood the handdbook spreadsheets-mkiv.pdf it is possible to define lua functions inside a cell. Who would you implement a max function that sets the value to 0 if it is negative? TIA juh P.S. For German speakers: We try to implement a Reisekostenformular.