[NTG-context] setuplist inherit margin and width

Hi, say, I want to design the TOC. Now I would write: \setuplist[LevelFour] [margin=1.20cm,width=0.5cm,...] \setuplist[LevelFive] [margin=1.70cm,width=0.5cm,] But is there some clever command that makes a calculation like this: \setuplist[LevelFour] [margin=1.20cm,width=0.5cm,...] \setuplist[LevelFive] [margin={\the\dimexpr\measure{margin[LevelFour]+width[LevelFour]}\relax},width=0.5cm,] Any idea? Thanks, Steffen