I currently have a large site navigation in the header of my site which links 3 levels deep in a large catalog of pages. I am going to be updating my website to silo the content and wish Google to not pass PageRank to most of these links but only to the second tier as these are content hubs and each represents a unique content silo (the top level is more for UI and are too generic to be content hubs).
When I am on one of these pages I wish to only pass PageRank to the sub pages of that tier and not to any of the other top tiers. The site is written on a custom code base so modifying HTML depending on the current page is easily done.
If anyone can tell me if and why "nofollow" wouldn't work that would be appreciated, if it does not work I certainly would like other suggestions.