[NTG-context] Index making

Hi all, Could some one tell me, why the index making in the following example does not come out as expected (as shown in the examplelines at the end)? \startluacode function Indexing(text) local data = text data = (string.gsub(data, ",", "+")) data = (string.gsub(data, "+ ", "+")) return data end \stopluacode \def\IndexItems#1{\index{\cldcontext{Indexing("#1")}}} \starttext We start with some text \IndexItems{Auto} We have then more text \IndexItems{Auto, motor} \IndexItems{Auto, carburator} Then we add non macro indexes: \index{Glass lamp} \index{Glass lamp+bulb} \index{Glass lamp+bulb+wire} \blank[3cm] \placeregister[index] \stoptext Thanks, Willi