A Shortcode to pull the next upcoming event and return 'Next course {start date} - Register'. You can set the category_slug parameter on the shortcode to pull a specific event category.

display_next_upcoming_event.php

<?php  // Please do not include the opening PHP tag if you already have one.

function display_next_upcoming_event( $attributes = array() )
{	
	$where_conditions = array(
	'Datetime.DTT_EVT_start' => array( '>=', EEM_Datetime::instance()->current_time_for_query( 'DTT_EVT_start' ) )
	);

	if (! empty($attributes['category_slug']) ) {
		$where_conditions['Term_Relationship.Term_Taxonomy.Term.slug'] = 'first';
	}

	$event = EEM_Event::instance()->get_one(
		array(
			$where_conditions
		)
	);

	if( $event instanceof EE_Event) {
		$datetimes = EEM_Datetime::instance()->get_datetimes_for_event_ordered_by_start_time( $event->ID(), false, false, 1 );
		$datetime = end($datetimes);
		if( $datetime instanceof EE_Datetime ) {
			$start_date = $datetime->start_date();
			$permalink = $event->get_permalink();

			return "Next course $start_date - <a href='$permalink'>Register</a>";		
		}
	}
}
add_shortcode('NEXT_UPCOMING_EVENT','display_next_upcoming_event');