PHP - Searchbar

I'm doing a site for a used vehicles company.  I have a "searchbar" with the following select options:  the first one is to search per vehicle manufacturer (ex. BMW).
The second one is for a price range (ex. any - $1 000 000). the third is per mileage (ex. any - 150 000). and the last one is per model (ex. 320).

All of them are structured as drop-down selectors except for the last one "model" which is has a input type text.  Here is what I struggle with... When I choose a manufacturer and click search then I get the desired results.  But as-soon as I choose a value from the price or mileage or model I get all the values from the manufacturer, but it doesn't filter what I have chosen.

Can you please help me....  Thank you

Here is the code for the searchbar.php:
Code: [Select]
<?php
?>

<form name="searchForm" action="showroom.php" method="GET" class="search">
<table cellpadding="0" cellspacing="0">
<tr class="search_bar">
<td><b>Search</b></td>
<td><select name="make">
<?php
do {  
?><option value="<?php echo $row_make['Make']?>"<?php if (!(strcmp($row_make['Make'], $row_make['Make']))) {echo "selected=\"selected\"";} ?>>
                <?php echo $row_make['Make']?></option>
            <?php
} while ($row_make = mysql_fetch_assoc($make));
  $rows = mysql_num_rows($make);
   if($rows > 0) {
       mysql_data_seek($make, 0);
   $row_make = mysql_fetch_assoc($make);
   }
?>
  </select> </td>
<td><select style="height:20px;" name="price">
<option>Price</option>
<option value="">Any</option>
                <option value="5000">R5,000 </option>
                <option value="10000">R10,000 </option>
                <option value="15000">R15,000 </option>
                <option value="20000">R20,000 </option>
                <option value="25000">R25,000 </option>
                <option value="30000">R30,000 </option>
                <option value="35000">R35,000 </option>
                <option value="40000">R40,000 </option>
                <option value="45000">R45,000 </option>
                <option value="50000">R50,000 </option>
                <option value="55000">R55,000 </option>
                <option value="60000">R60,000 </option>
                <option value="65000">R65,000 </option>
                <option value="70000">R70,000 </option>
                <option value="75000">R75,000 </option>
                <option value="80000">R80,000 </option>
                <option value="85000">R85,000 </option>
                <option value="90000">R90,000 </option>
                <option value="95000">R95,000 </option>
                <option value="100000">R100,000 </option>
                <option value="125000">R125,000 </option>
                <option value="150000">R150,000 </option>
                <option value="175000">R175,000 </option>
                <option value="200000">R200,000 </option>
                <option value="225000">R225,000 </option>
                <option value="250000">R250,000 </option>
                <option value="275000">R275,000 </option>
                <option value="300000">R300,000 </option>
                <option value="325000">R325,000 </option>
                <option value="350000">R350,000 </option>
                <option value="375000">R375,000 </option>
                <option value="400000">R400,000 </option>
                <option value="425000">R425,000 </option>
                <option value="450000">R450,000 </option>
                <option value="475000">R475,000 </option>
                <option value="500000">R500,000 </option>
                <option value="600000">R600,000 </option>
                <option value="700000">R700,000 </option>
                <option value="800000">R800,000 </option>
                <option value="900000">R900,000 </option>
                <option value="1000000">R1,000,000 </option>
  </select> </td>
<td><select style="height:20px;" name="mileage">
<option>Mileage</option>
<option value="0_10000">0-10 000 km</option>
                <option value="10001_20000">10 001-20 000 km</option>
                <option value="20001_30000">20 001-30 000 km</option>
                <option value="30001_40000">30 001-40 000 km</option>
                <option value="40001_50000">40 001-50 000 km</option>
                <option value="50001_60000">50 001-60 000 km</option>
                <option value="60001_70000">60 001-70 000 km</option>
                <option value="70001_80000">70 001-80 000 km</option>
                <option value="80001_90000">80 001-90 000 km</option>
                <option value="90001_100000">90 001-100 000 km</option>
                <option value="100001_110000">100 001-110 000 km</option>
                <option value="110001_120000">110 001-120 000 km</option>
        <option value="120001">120 000km and above</option>
  </select></td>
<td align="right"><b>Model:</b></td>
<td><input type="text" name="model" /></td>
<td><input type="submit" value="Search" /></td>
</tr>
</table>
</form>