Tracking changes

I have an idea for tracking changes in a drawing but before I write a
routine I wondered if there was something out there already. If you save
the last entity handle when you close a drawing and the first entity handle
when you open the same drawing you can can track all of the entities that
were added between sesisons. I need something like this to track changes
and who made them. I'd like to be able to parse through a list of changes
by highlighting the enties for each session but I don't know how to select
entities by their handles? Does anyone have any suggestions?

 

;; Tracking changes in a large drawing almost impossible.
;; You can not highlighting entities inside block .
(mapcar '(lambda (X)
(redraw (handent X) 3)
)
'("4A4F" "4A4E" "4A4D") ;handle list
)