[NTG-context] Float references in a register

Is it possible to have float references (i.e. Table 1.1) alongside page numbers in a register? I've never come across it before, but I've just been asked to produce an index which has entries like: coverage measurement tools 176-177, Table 6.5 I have looked through core-reg without much illumination. I wonder if I can use \writetoregister but experiments thus far haven't been successful. Is this sort of thing supported/supportable? Thanks, Duncan