I don't think it's possible with a macro. Something like this will not work:
#macro Item(name)
#ifdef(name)
do_whatever_with name
#end
#end
because 'name' _is_ always defined in the context of the macro.
--
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):5;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/
