How to redirect to a differnt page based upon the Role's for the user....

Hello guys,
I have a web application and based upon the roles of the user i give access to different tabs...Let's say a particular user x doesn't have a role y then he cannot access z tab....but here is the problem  if the user clicks the z tab it gets to Login page....How do i redirect it to a different page which says something like "Your account doesn't have access to view this section"
 
Thanks,
Chetan
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