How to intercept double click event on a folder on osx?

How to intercept double click event on a folder on osx?

experts. what I want is like this: I create a folder named RootDir, then I
double click the folder in Finder , I hope I can intercept the action and
trigger specific action such as mounting this RootDir to another folder
named MountDir and then open MountDir, not RootDir. how should I do it
(Using objective-c)? my platform is mountain lion (osx10.8) and I've tried
using fsevent to monitor, but i don't think i can catch the action of
folder open/close.... and is it the only way for me to use Finder
injection to achieve this function? any suggestions would be appreciated.