Hi Alberto,
I've previously looked and installed RT-Extension-MandatoryFields but it
only seems to enforce the field(s) to be filled, what I'm looking for is a
way to validate the date entered, in my case I'd like to limit Priority to
an integer between 0 and 100, anything besides number and past
I think this is exactly what you are looking for
http://search.cpan.org/dist/RT-Extension-MandatoryFields/
There are also two more specific extensions:
http://search.cpan.org/dist/RT-Extension-MandatoryRequestor/
http://search.cpan.org/dist/RT-Extension-MandatorySubject/
BTW I suggest you to loo