ทำไงให้ List Box เวลาเลือกข้อมูลไปแล้ว ข้อมูลนั้นจะไม่ขึ้นมาโชว์ อีก

<?php
<tr bgcolor="#FFFFFF">
          <td height="8" colspan="2" valign="top" bgcolor="#FFFFFF" align="left"><form id="form_download" name="form_download" method="post" action="download2.php">
            <br />
            <table width="333" border="0" align="center">
              <tr>
                <th colspan="2" scope="row"><p align="center">                  Download</p>                  </th>
                </tr>
              <tr>
                <th width="128" scope="row">&nbsp;</th>
                <th width="248" scope="row">&nbsp;</th>
              </tr>
              <tr>
                <th background="images/ses-line2.gif" scope="row"><div align="center">ประเภท</div></th>
                <th scope="row">      
                  <div align="left">
             <?
//************************* เลือก ประเภท *************************//
			  if(isset($_GET['cat_id'])) //ถ้ามีการส่งค่าตัวแปร cat_id ผ่าน URL
			  { 
			  echo "<font color=blue>".$cat_name;
			  }
			  else
			  		{  //else category?>
					<select name="category" class="BorderStyle" id="category" onChange="MM_jumpMenu('parent',this,0)">
                      <option>:: เลือกประเภท ::</option>                    
                      <?
  						$clsMyDB->strTable = "eo_category";
						$resultList1 = $clsMyDB->fncSelectRecordAll();
						if(!$resultList1)
							{
								echo "Category ... not found<br>";
								exit();
							}
						else
							{
								foreach ($resultList1 as $eachResult1)  
        							{  ?> 
                      					<option value="download.php?cat_id=<? echo $eachResult1['cat_id']; ?>&cat_name=<? echo $eachResult1['cat_name']; ?>"> <? echo $eachResult1['cat_name']; ?></option>
						<? } } ?>
                    </select>
					<?  }  //else category
//***************************************************************//
			  ?>                  
                  </div></th>
              </tr>
			  <?  if(!isset($_GET['cat_id'])) { echo "<tr><th scope=row>&nbsp;</th><th scope=row>&nbsp;</th></tr><tr><th scope=row>&nbsp;</th><th scope=row>&nbsp;</th></tr><tr><th scope=row>&nbsp;</th><th scope=row>&nbsp;</th></tr>"; }
			  if(isset($_GET['cat_id']))  { // - -  ?>
              <tr>
                <th height="21" background="images/ses-line2.gif" scope="row"><div align="center">ลุกค้า</div></th>
                <th scope="row">		
                <div align="left">
                <?
//************************* เลือก ชื่อลูกค้า *************************//				
				if(isset($_GET['customer_id']))
				{ 
				 $customer_id =  $_GET['customer_id'];    
				 $customer_name = $_GET['customer_name']; //.ให้เก็บค่าไว้ในตัวแปร
			     echo "<font color=blue>".$customer_name;
			  }
			  else
				{ //else Customer
				?>
                  <select name="customer" class="BorderStyle" id="customer" onChange="MM_jumpMenu('parent',this,0)">
                    <option>:: เลือกลูกค้า ::</option>
                    <?
  						$clsMyDB->strTable = "eo_customer";
						$resultList2  = $clsMyDB->fncSelectRecordAll();
						if(!$resultList2)
							{
								echo "Customer ... not found<br>";
								exit();
							}
						else
							{
								foreach ($resultList2 as $eachResult2)  
        							{  ?>                     
                    					<option value="download.php?cat_id=<? echo $cat_id; ?>&cat_name=<? echo $cat_name; ?>&customer_id=<? echo $eachResult2['customer_id']; ?>&customer_name=<? echo $eachResult2['customer_name']; ?>"><? echo $eachResult2['customer_name']; ?></option>
                            <? } } ?>
                  </select>
                  <?  } //else Customer
//***************************************************************//
			  ?> 
                </div></th>
              </tr>
              <?  if(!isset($_GET['customer_id'])) { echo "<tr><th scope=row>&nbsp;</th><th scope=row>&nbsp;</th></tr><tr><th scope=row>&nbsp;</th><th scope=row>&nbsp;</th></tr><tr><th scope=row>&nbsp;</th><th scope=row>&nbsp;</th></tr>"; }
			  if(isset($_GET['customer_id'])) {  // - - ?>
              <tr>
                <th height="21" background="images/ses-line2.gif" scope="row"><div align="center">โมเดล</div></th>
                <th scope="row">
                <div align="left">
                <?
//************************* เลือก โมเดล *************************//
				if(isset($_GET['model_id']))
				{ 
			      echo "<font color=blue>".$model_name;
			    } else 
				   { //++
				?>
                    <select name="model" class="BorderStyle" id="model" onChange="MM_jumpMenu('parent',this,0)">
                      <option>:: เลือกโมเดล ::</option>
                      <?
  						$clsMyDB->strTable = "eo_model";
						$clsMyDB->strCondition = " cat_id='$cat_id' AND customer_id='$customer_id' ";
						$resultList3  = $clsMyDB->fncSelectRecordAlls();
						if(!$resultList3)
							{
								echo "Model ... not found<br>";
								exit();
							}
						else
							{
								foreach ($resultList3 as $eachResult3)  
        							{  ?>
                      <option value="download.php?cat_id=<? echo $cat_id; ?>&cat_name=<? echo $cat_name; ?>&customer_id=<? echo $customer_id; ?>&customer_name=<? echo $customer_name; ?>&model_id=<? echo $eachResult3['model_id']; ?>&model_name=<? echo $eachResult3['model_name']; ?>"><? echo $eachResult3['model_name']; ?></option>
                              <? } 
							  } 
					  ?>
                    </select>
              <?  } //++
//***************************************************************//
			  ?> 
                </div></th>
              </tr> 
              <tr>
                <th scope="row">&nbsp;</th>
                <th scope="row">&nbsp;</th>
              </tr>
            </table>  
            <br />
            <center><input name="send" type="submit" class="MenuStyle" value="ตกลง" />
            </center> 
            <br />
            <input name="cat_id" type="hidden" value="<? echo $cat_id; ?>" />
            <input name="cat_name" type="hidden" value="<? echo $cat_name; ?>" />
            <input name="customer_id" type="hidden" value="<? echo $customer_id; ?>" />
            <input name="customer_name" type="hidden" value="<? echo $customer_name; ?>" />
   			<input name="model_id" type="hidden" value="<? echo $model_id; ?>" />
            <input name="model_name" type="hidden" value="<? echo $model_name; ?>" />
            <!--l --------------------------------------->
          </form>
          <? }  }  // - -  ?>
          </td>
        </tr>
?>