Helper function: basic equivalent to update_post_meta() but targeting the ECP custom field implementation

update_ecp_custom_field.func.php

<?php
/**
 * Updates an Events Calendar PRO-style custom field.
 * 
 * @param int    $post_id
 * @param string $field_label
 * @param string $value
 */
function update_ecp_custom_field( $post_id, $field_label, $value ) {
	$custom_fields = (array) tribe_get_option( 'custom-fields' );
	$field_name    = '';

	foreach ( $custom_fields as $field_structure ) {
		if ( $field_label === $field_structure['label'] ) {
			$field_name = $field_structure['name'];
			break;
		}
	}

	if ( ! empty( $field_name ) ) {
		update_post_meta( $post_id, $field_name, $value );
	}
}