Right now Drilldown can only be set on the data source. However, some crucial tables are often missing a drilldown form/page.
Instead of having them either not working or just setting the data grid and giving up on NAV drilldown altogether, it would be nice to be able to catch this in the NL function. e.g.
=NL("Rows";"Sales Line";;"Drilldown=";"Jet Data Grid")