Fai cosi....

codice:
$codice   = "";
$continua = $row_act = mysql_fetch_array($result_act);
while ($continua) {		
 $codice .= "<a>{$row_act['act_surn']} {$row_act['act_name']}</a>";
 $continua = $row_act = mysql_fetch_array($result_act);
 if ($continua) {
  $codice .= " - ";
 }
}

print $codice;