[NTG-context] texexec --pdfselection with selection range

Hello, how I can use TeXExec --pdfselection with a selection range? If I try --selection=3-50,52-90 I get an error. It works if I write --selection=3,4,5,6,7,... but this is quite labourous and one needs to make sure that one has not forgot a single number. (I try to cut out the colour pages to save some paper (60 sheets) while printing to the b/w printer.) Tobias