How to enable / disable sidebar?

Hi,

I have created a sidebar which looks like this:

function customSidebar(){
    register_sidebar(array(
        'name' => 'Custom Sidebar',
        'id' => 'sidebar-3',
        'before_widget' => '<li id="%1$s" class="widget %2$s">',
        'after_widget' => '</li>',
        'before_title' => '<h2 class="widgettitle">',
        'after_title' => '</h2>',
    ));
}

This works absolutely fine and I can see my widget when I go to Appearance -> Widgets.

But I would like to have the option to enable or disable that sidebar whenever I want on any post.

How can I do that?