$string = '12141441,14414141,41466464';
$params = array_unique(explode(',',$string));
$params_count = count($params);
if($params_count>0){
 if($in_or_union){
   $sql = "SELECT filed1, field2, field3 FROM table1 WHERE field1 IN (".trim(str_repeat(" ?,",$params_count) ,',').")";
 }else{
  $sql = "SELECT filed1, field2, field3 FROM table1 WHERE field1 = ?";
  $sql_union = implode("\r\nUNION\r\n",array_pad(array(),$params_count,$sql));
  $sql = $sql_union;
 }
 $rs = $DB->Execute($sql,$params);
 while(!rs->EOF){
  ...
 } 
}