Is it possible to modify GNATS to restrict possible STATE changes ?

[COX, Sam]

Im just starting out with GNATS 3.xx and I am wondering how configurable it
is. What I am looking for is a way to restrict the possible state chages
based on the current state. Basically to stop the possibility of going
straight from OPEN to CLOSED and missing all the intermediate steps. 

It looks like no simple configuration file change could achieve this. What
is my next step? Is it possible to execute scripts withing GNATS that could
test the state before making a change?  

If not, what (in general terms) is required to modify the program itself? Is
it possible at all? 

Any help would be appreciated.