Thanks for the quick answers. Both suggestions work for me. @Massi Thanks for the pointer into the cld-mkiv.pdf @Wolfgang: I have to admit that I don't completely comprehend your solution, though it works. Searching around for the commands you use, I came across an older posting you answered too: https://mailman.ntg.nl/pipermail/ntg-context/2012/064326.html That helps too. However I can find little documentation on the \setvariable/s commands. I'll play around with the solution to understand it better.
\defineexpandable\question{44}
A solution which uses only existing commands in the document.
\startsetups [martin] \startlua local points = tonumber(\getvariable{martin}{question}) or 0 ; points = points * 92 ; local answer = 42 ; context.setvariable("martin","points",points) ; context.setvariable("martin","answer",answer) ; \stoplua \stopsetups
\setvariable{martin}{set}{\directsetup{martin}}
\starttext
\setvariables [martin] [question=44]
Points: \getvariable{martin}{points}
The answer is \getvariable{martin}{answer}.
\stoptext
Wolfgang