Rules, triggers and such

Hello all again :)

I have a question: is it possible to replicate the behavior of a rule
INSTEAD of with a TRIGGER?

For some specific reasons i need to use a trigger to update a
secondary table, but i don't want the changes to happen in the primary
table too.

Is it possible to do it? If so, how?

I thought of using a instead of rule with a procedure, but a trigger
is just so much easier :P

Thanks

--
George R. C. Silva

Desenvolvimento em GIS
www.sextantegeo2.blogspot.com