Hugo,
Sounds like you needd to do some reading on the capabilities of your
tool. If you don't know how to do multiple rules then you are just playing
at it. 8^>
Not sure which version of AD you have but you need to check out the learning
guides available for download through the Altium website. Like:
http://www.altium.com/community/support/learningguides/altiumdesigner6learningguides/
TR0116 Design Rules Reference
or
http://www.altium.com/Community/Support/LearningGuides/AltiumDesigner2004LearningGuides/
AR0111 Specifying the PCB Design Rules and Resolving Violations
and
TR0116 Design Rules Reference earlier DXP2004 version than the one listed
above.
And there are many, many more, a couple of dozen. There are also some of
these available on your computer right now through the "About" drop-down
menu area.