[NTG-context] Filling framed boxes up to the max

Hi, I would like to do the timetable of the Chaos Communication Congress in ConTeXt again. Last year, I used a perl script to convert the iCal file to ConTeXt code. This year, I'd like to do it a bit better. One of the problems I have there is that I would like to fill a framed box with text up to the max. If it is full before everything is typeset, the text should end with »...«. The manual solution (cf. http://www.alech.de/tmp/day1.pdf) involved counting the numbers of letters and perl and estimating a cut-off value. But I guess there is a better method in ConTeXt itself. Maybe someone here has an idea. TIA, Greetings, Alex