Book

Has anybody managed to get activity locking working with the Book module? I want my students to be prevented from accessing a book until they have completed a previous activity. I have activity locking working beautifully with resources and assignments but no luck with book or chat modules. I have tried inserting the activity locking code into the book/view.php file as follows:

    /// Activity Locking ///
    require_once($CFG->libdir.'/locklib.php');
    check_locks($cm);
/// End Activity Locking ///

I have tried inserting it in several different places, but nothing seems towork. In the assignments and resources modules this code is inserted at the end of the file between the lines:

require_login($course->id);

and

require ("$CFG->dirroot/mod/assignment/type/$assignment->assignmenttype/assignment.class.php");

But these lines do not exist in the book module and I am now completely stuck!

Any suggestions welcomed!!!

Nikki Macfarlane