Adding a command to the "final" expression evaluation?

Hey all.  Does anyone know if there is an "approved" way for me to tell
Maxima to run an extra command on every expression at the end of an
evaluation?  The normal defining of simplification rules won't work for
what I need, I've tried.  What I WANT to have happen is:

%i1 3kg*m^2/s^2;
%o1 3*N*m

without any extra work on the part of the end user (once the initial
command is given to activate units, of course.)  This sort of thing is
only doable via ratsubst, and may need to be done multiple times
depending on conditions, so what I need is a way to add a
processunits(%finalexpression) to the main loop.  I could try to
hackishly do it myself, but I would prefer to use some kind of
"approved" method.  What would be the best practice in a case like
this?

Thanks,
CY


		
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