hi
we have done this in small excel programming for our own ticketing system not solution manager.
the use case is very simple, as my manager wants to track the processors who holds the ticket long time without process 
But you can do this in solman too, try this Solution Manager Service Desk Time Recording
if doesnt help, you need to look for status change timings manually in table and create your own z.
pls check.
Thanks
Jansi