Restrict Author role to only 3 wp-admin pages

Question

I allow the author user role to add/edit posts (using a custom post type called "User Posts") as well as add/edit their own media from wp-admin. I currently have it set up so that the only menu items they see are the "User Posts" "New User Post" "Media" and "Upload Media", with these URLs: post-new.php?post_type=tsv_userpost edit.php?post_type=tsv_userpost upload.php media-new.php

The only problem is that if the user types in the URL of, for instance, post-new.php (without the custom post type part) Wordpress still allows them to see that page. No bueno.

Is there a way to redirect or display an error message to users if they are not admins and if they land on any wp-admin page EXCEPT the above URLs?

I have tried using this code (just for the post-new.php page) from another thread, but it doesn't seem to do anything:

//Show error message if authors try to access wrong wp-admin pages
add_action('admin_head','my_restrict_access');
function my_restrict_access_meassage(){
    global $pagenow;
    if ($pagenow == 'post-new.php' && !current_user_can( 'switch_themes' )){
        echo '<div class="wrap"><br />
            <div id="message" class="error">You Dont have the right permissions to access this page</div>
        </div>';
        exit();
    }
}

Thanks is advance.

EDIT: Here's the code I ended up with that works:

        //Restrict access to authors in wp-admin pages
    //Show error message if authors try to access wrong wp-admin pages
    add_action('admin_head','my_restrict_access');
    function my_restrict_access(){
        $Path=$_SERVER['REQUEST_URI'];
        $basepath='http://www.theseattlevine.com/wordpress/wp-admin';
        $URI='http://www.theseattlevine.com'.$Path;

            if      (   ($URI ==($basepath . '/post-new.php')) && !current_user_can ('manage_categories') ) {
                        echo    '<div class="wrap"><br />
                                    <div id="message" class="error">You Dont have the right permissions to access this page. Try these links instead: 
                                        <ul>
                                            <li><a href="/">The Vine Homepage</a></li>
                                            <li><a href="/wordpress/wp-admin/post-new.php?post_type=tsv_userpost">Add a new user post</a></li>
                                            <li><a href="/dashboard">Your dashboard</a></li>
                                        </ul>
                                    </div>
                                </div>';
                        exit();
                        }
            elseif      (   ($URI ==($basepath . '/edit.php')) && !current_user_can ('manage_categories') ) {
                        echo    '<div class="wrap"><br />
                                    <div id="message" class="error">You Dont have the right permissions to access this page. Try these links instead: 
                                        <ul>
                                            <li><a href="/">The Vine Homepage</a></li>
                                            <li><a href="/wordpress/wp-admin/post-new.php?post_type=tsv_userpost">Add a new user post</a></li>
                                            <li><a href="/dashboard">Your dashboard</a></li>
                                        </ul>
                                    </div>
                                </div>';
                        exit();
                        }

    }

Answer 1

Make sure that the second parameter in the "add_action" function matches the name of your restrict access function. It should look something like this:

add_action('admin_head','my_restrict_access'); 
function my_restrict_access(){ /* code as before */ } 

Glad I could help. :)