Hello Arakesh!
You're looking for Aspect Oriented Programming. The Spring.NET framework is open source (won't cost you a cent (or a penny)) and can
be used for AOP (aspect oriented programming). As far as I know the configuration is pretty straight forward and even patterns can be used
to declare the point cuts.
Here a link I suggest to read up on this:
http://static.springsource.org/spring/docs/2.0.x/reference/aop.html
This might be the way to go for you. If you have any doubts check back with me.
Cheers
Manfred