about selection screen

1. I am having two selection frames in the selection screen, in the firest selection screen i am having Date,Purchase order, Vendor, City fields and in the second frame i having 3 radio buttons with Date, P.order, Vendor, if i select one radio buttion in the second frame i need to remain highlight the fields related to that radiobutton rest of them should be hide. How can u write logic for this?

2. Is it possible to create inner join between two cluster tables and

is it possible to create inner join between two pooled tables?