New first-class Ticket field

Sorry if this is newbish. I am trying to add a simple
feature to RT which will track a CallTime parameter in
Tickets in addition to the TimeWorked parameter. I
want to implement it exactly like TimeWorked, where the
ticket will have an overrall CallTime, and each
Transaction will have a CallTimeTaken which will add to
the overrall CallTime for the corresponding Ticket.
Because I want to track CallTime in this way, I don’t
want to implement it as a custom field. The database
schema and html UI are easy enough to update to handle
the additional field. What I am trying to get my head
around is the proper way to update the Perl source in
under lib/RT to take care of this new field, without
screwing up any auto-generated files or anything like
that. Has anyone done something like this and would
like to give me a brief overview ? Thanks for sharing.

– Matt Meyer