[NTG-context] Index design

Hi, in a index is it possible not to have bold letters as separators ("a", "w") in a dedicated line, but instead only the first letter of the first entry with "a" or "w" bold? See this minimal example: \starttext \chapter{First Chapter} Some text...\index{word} \section {First Section} Some text...\index{word} Some text...\index{another word} Some text...\index{another word} \page[yes] \completeindex \stoptext Here I would like to have only the first letter of the index entries "another" and later "word" in the index to be set bold. (Hope you understand what I mean...) Thanks, Steffen