How to Make this section of code into a function

I have this code in my header.php. Basically I widget-ized the navigation menu area, but if there are no widgets active, I have it revert to the normal nav menu.

<?php if ( ! is_active_sidebar( 'nav-widgets' ) ) {

				wp_nav_menu( array( 'theme_location' => 'primary', 'menu_class' => 'nav-menu' ) );

} else {
    				?> <div id="nav-widgets"> <?
    				dynamic_sidebar('nav-widgets');
    				?> </div> <?
} ?>

I’d love if someone could show me how to convert this into a function and then call it in the appropriate place in header.php.