class.tx_next_address_sort_addmarkers.php:
<?php
class tx_next_address_sort_addmarkers {
	function extraItemMarkerProcessor(&$markerArray, &$address, &$lConf,
		&$pObj) {

		$lcObj = t3lib_div::makeInstance('tslib_cObj');
		$lcObj->data = $address;

		$markerArray['###SORTBEREICH###']   =
		$lcObj->stdWrap($address['next_address_sort_sort_bereich'],
		$lConf['next_address_sort_sort_bereich.']);

	}

}

-------

ext_localconf.php:
<?php
$GLOBALS['TYPO3_CONF_VARS']['EXTCONF']['tt_address']['extraItemMarkerHook'][]
='EXT:next_address_sort/class.tx_next_address_sort_addmarkers.php:tx_next_address_sort_addmarkers';