🚀 go-pugleaf

I'm stymied.  What I'm trying to do is get latex to put a custom header in
my document modelled as follows:

TOPIC                                                                     P
---------------------------------------------------------------------------

Where `TOPIC' is the current document section (which can be changed by
changing the value of a new variable, say, \headtopic), `P' is the
current page number, and the line goes from the left margin to the right
margin.  Of course, I'd like to get it to do twosided printing, so for even
pages, things would be switched, or vice-versa.  I've tried the \markboth
command with \pagestyle{myheadings}, but cannot figure it out.

Is there an easy (any?) way to do this with article document style?

Thanks for any help, Andy B