[NTG-context] setupregister with realpage?

Dear list, \setuplist has the convenient option [pagenumber=realpage] \setupregister has not (yet). How can I get the realpagenumber instead of the userpagenumber for the register indices? I tried \def\MyPageCommand#1{\realpagenumber} \setupregister[MyIndex][pagecommand=\MyPageCommand] but this prints only the current (although real) page number. Thank you! Benjamin