Before report trigger

I have to create a before report trigger which have to return a value and this value will be used in my SQL Query again. In reports Builder I assigned a value (by calling a function) to a user parameter.

E.g

Function BeforeReport return boolean is

BEGIN

  hr_standard.event('BEFORE REPORT');

  : p_profile_value := fnd_profile.VALUE('RESP_ID');

END;

How do I do this now in a XML Data Template?