finer granularity on changing fields

[Don Shesnicky]

Sorry if this is already discussed somewhere but the search page is
giving 
a "Internal Server Error"....
 
My company is looking for finer granularity on the ability to limit
users 
to change fields. For instance only team leaders would be able to set
priority 
or perhaps close the ticket. I have 2.16.5 installed and only see the
"Bit 32 
editbugs Can edit all aspects of any bug" group. 
 
Is this functionality already built into this  version of bugzilla and
I'm 
missing it somewhere? 
 
Is there the ability to add more bits/groups that I could edit the code 
to check?
 
I believe I see the sub that needs modification CheckCanChangeField,
don't 
fully understand it yet though.
 
Don