อยากทราบวิธีการค้นหาราคาสินค้าจาก listbox อะครับไม่รู้ว่าทำยังไง

 <select name="slprice" class="style113" id="slprice">
          <option value="0" selected="selected">ทุกราคา</option>
          <option value="1">1-50 บาท</option>
          <option value="2">51-100 บาท</option>
          <option value="3">101-200 บาท</option>
          <option value="4">201-300 บาท</option>
          <option value="5">301-500 บาท</option>
          <option value="6">501-1000 บาท</option>
          <option value="7">มากกว่า 1000 บาท</option>
          </select>

     <? 
	  $slprice = $_POST ["slprice"];			
	  				if($_POST ["slprice"] == "1"){
						$moneyslprice = "pd_price < 50";}
					else if($_POST ["slprice"] == "2"){
						$moneyslprice = " and pd_price >= 50 and pd_price <= 99";}
					else if($_POST ["slprice"] == "3"){
						$moneyslprice = " and pd_price >= 100 and pd_price <= 199";}
					else if($_POST ["slprice"] == "4"){
						$moneyslprice = " and pd_price >= 200 and pd_price <= 299";}
					else if($_POST ["slprice"] == "5"){
						$moneyslprice = "and pd_price >= 300 and pd_price <= 499";}
					else if($slprice == "6"){
						$moneyslprice = " and pd_price >= 500 and pd_price <= 999";}
					else if($slprice == "7"){
						$moneyslprice =" and pd_price > 1000";}
						else if($slprice == "8"){
						$moneyslprice =" and pd_price = 0";}
						else{
$moneyslprice = "";}
						?>
  </tr>
</table>
<?
		$objConnect = mysql_connect("localhost","otop","1234") or die("Error Connect to Database");
		$objDB = mysql_select_db("otop");
	// Search By Name or Email
		$strSQL = "SELECT * FROM product WHERE product.pd_ctg_id = '". $colname_rs_pr_name . "'";
		echo $strSQL;
		echo $objQuery;
		echo $_POST["slprice"];
		echo $moneyslprice;
		echo $_POST["txtname"];
	if($_POST["slprice"] != "")
	{
	 $strSQL .= " AND pd_price = '$moneyslprice'";
	}	
		if($_POST["txtname"] != "")
	{
	 $strSQL .= " AND (pd_name LIKE '%".$_POST["txtname"]."%') ";
	}
		$objQuery = mysql_query($strSQL) or die ("Error Query [".$strSQL."]");
	?>