Am 22.04.2013 um 23:28 schrieb Jan Heinen :

Thank you all!!!!!!

My book from last year (15.000 lines text + context-code and 1.500 lines macro-code now was compiled without no further problems!

I only had to change all \define\variable ...

to \defineexpandable\variable ...

I think, now I understand a little bit more about ConTeXt and try again to give a little bit back to the community. I have started a new article on the context-wiki:

http://wiki.contextgarden.net/Calculating_with_dimension_units

Hopefully the more sophisticated ConTeXter help a little bit to improve the article. Please have a look what is wrong and what I have forgotten (or don't know).

The Lua version can be removed because the line \defineexpandable\ColumnABii {\ctxlua{context([==[\ColumnA + \ColumnB]==])}} is only a complicated form to write \defineexpandable\ColumnABii {30mm + 40mm} What does happen is that context replaces \ColumnA with 30mm and \ColumnB with 40mm but nothing is calculate because the argument is a simple text string. Wolfgang