As a scripted solution, you could use a signal to do this, with the use of a couple of aliases for var and set.
alias var { var $1- | signal varchange var $1- }
alias set { set $1- | signal varchange set $1- }
Or something along those lines, parsing the data would be a little more work because of the various var/set formats that can be used, but it is certainly doable.
