How to change the FND USER password with Old password using PL/sql script

BEGIN
   fnd_user_pkg.changepassword ('USERNAME', 'OLDPASSWORD', 'NEWPASSWORD');
END;
  Input (Mandatory)
  username:       User Name
  oldpassword     Old Password
  newpassword     New PasswordExample:-
DECLARE
   x   BOOLEAN;
BEGIN
   x := fnd_user_pkg.changepassword ('SHIBANI', 'shibanikutty', 'welcome');
END;