BROWSE - Replace Country to City

I want to replace the browse by country to browse by city in the Browse profiles page.

I tried modifying these lines in bxbasebrowse.php        

if ( isset($oObject -> aMembersInfo[$sCurrentKey]['city']) ) {

                $aCurrentArray    = &$oObject -> aMembersInfo[$sCurrentKey]['city'];

But the city block appears empty, am I missing something?

Thanks

-T