Pre and Post GC functions

[verzullj@cs.rpi.edu (Joseph Verzulli)]

I need to have a function called just before each garbage collection, and
another function called just after garbage collection.  I tried redefining
CCL:GC to do this (it first calls my function, then calls the old ccl:gc,
then calls another of my functions).  This works when I manually invoke
(GC), but is ignored when Lisp automatically does a GC.  Is there another way
to do this?