\setupreferencing[autofile=yes]

\useexternaldocument[foo] [setnumber-001] [{TEST 1}]

\setupheadnumber[chapter][\getreferencesectionnumber{foo::two}]

\starttext

    \chapter[three]{Three} from setnumber-001, one: \getreferencesectionnumber{foo::one}\par
    \chapter[four] {Four}  from setnumber-001, two: \getreferencesectionnumber{foo::two}\par

\stoptext
