[texhax] Headline numbering problem

[Rodolfo Medina]

Hi all.

I use plain TeX and have defined my own \chapter, \subchapter etc.  Now, my
problem is that right at the bottom of p.11 the subchapter 2 ends, and right at
the top of p.12 the subchapter 3 begins, but in the headline of p.11 there is
subchapter 3.  Here is (extremely summed up) the definition of \headline I'm
using:

  \headline={\the\subchapternumber}

Does anybody have any suggestion about this matter?
Thanks,
Rodolfo