Drop Down Filter 'Not Working'

Hi,
Taken from the manual I dont appear to be able to get the filtering right?
I have a specific table essesntial Month and Year. (This gets updated each month automatcally).
The list is created accordingly and when you select a month the filter does not filter the months?
The column on the default list page that contains the data (ie Month and year) is called 'Tax Point'
OK I am missing the obvious no doubt but any ideas/help appreciated...........
In bold values I currrently have.
//create dropdown box
$str = "";
$str.= "<select onchange=\"window.location.href=this.options[this.".
"selectedIndex].value;\"><option value=\"\">Please select</option>";
//select values from database
global $conn;
$strSQL = "select month from datetable";
$rs = db_query($strSQL,$conn);
while ($data = db_fetch_array($rs))
$str.="<option value=\"main_default_page_list.php?ctlSearchFor=".$data["month"].
"&srchOptShowStatus=1&ctrlTypeComboStatus=0&srchWinShowStatus=0&a=".
"integrated&id=1&criteria=and&type1=&value11=".$data["month"].
"&field1=company&option1=Contains&not1=a=search&value=1\">".
$data["company"]."</option>";
$str.="</select>";
echo $str;