[NTG-context] How to print all pages for a single index entry?

I have an index like this: \starttext \index{butterflies}\index{horses}\index{cows} \placeindex \stoptext The placeindex will place every index. Is there a way to say, display an index, but only for a specific single entry, or specific list of entries, e.g. \placeindex[horses, cows] (would exclude butterflies from the index entries) --Joel