how to preview an image file in this code

[thread_PHP]

Hi all
I have a problem. i am using adodb using mvc connection in php my page will get me the rows from the table where id =1 i need to replace the image file if it is exist. please help me anybody

 <script language="javascript">
function DoPreview()
{

  var filename = document.form1.btnLogoFile.value;
alert(filename);
  var Img = new Image();

  if (navigator.appName == "Netscape")
  {
    alert("Previews do not work in Netscape.");
  }
  else
  {
    Img.src = filename;
    document.images[3].src = Img.src;
  }
}
function show_table(showid)
{


  if(showid=="horizontal"){
  horizontal.className='visibleError';
  //vertical.className='hiddenError';
   }
 }	
function check()
  {
var v =document.getElementById('horizontal');

	alert(v.className);



      if(document.form1.bname.value == "")
    {
            alert("Please Enter Business Name");
            document.form1.bname.focus();

			 return false;
    }


   if(document.form1.cname.value == "")
    {
            alert("Please Enter Contact Name");
            document.form1.cname.focus();
             return false;
    }



     /* if((document.form1.eadd.value == "")||(document.form1.eadd.value.indexOf('@') == -1) || 
(document.form1.eadd.value.indexOf('.') == -1))
        {
                alert("Please Enter Email Address");
                document.form1.eadd.focus();
                 return false;
        }*/

     if(v.className == 'visibleError')
	 {
	 	  if(document.form1.oldpass.value == "")
    		{
            alert("Please Enter old password Name");
            document.form1.oldpass.focus();
             return false;
    		}
			  if(document.form1.newpass.value == "")
    			{
            alert("Please Enter new password Name");
            document.form1.newpass.focus();
             return false;
    			}

				  if(document.form1.repass.value == "")
    			{
            alert("Please Re Enter new password Name");
            document.form1.repass.focus();
             return false;
    			}

		 if(document.form1.newpass.value != document.form1.repass.value)
    			{
            alert("ranjtih");
            document.form1.repass.focus();
             return false;
    			}



	 } 
	 return true;
}
</script>  
<form name="form1" method="post" action="processupdate.php" enctype="multipart/form-data">
<table width="80%"  border="0" cellspacing="0" cellpadding="0">
  <tr>
    <th scope="row">Business Name</th>
    <td>&nbsp;</td>
    <td>

 <?php




 $selectcouponlist = "SELECT businessname, contactname, address,email,company_logo,isadmin,date_created,date_modified FROM coupon_users WHERE user_id = 1";

$ADODB_FETCH_MODE = ADODB_FETCH_ASSOC;
$couponlist = $db->Execute($selectcouponlist);

if($couponlist === false) die('query failed');
if($couponlist->RecordCount() < 1)
	echo "<tr><td colspan='4'>No Coupons Found</td></tr>";
else {
#		rs2html($couponlist);
#		Coupon Title	Coupon Created By	Status	Delete
		$couponset = $couponlist->GetRows();
		foreach($couponset as $coupon) {
				/*echo "<tr>";		
				echo "<td>".$coupon['businessname']."</td>";
				echo "<td>".$coupon['contactname']."</td>";
				echo "<td><a class='tbllinks' href='mailto:".$coupon['email']."'>".$coupon['email']."</a></td>";
				echo "<td>".$coupon['subscriber_id']."</td>";*/
/*
				echo "<td>".$coupon['coupon_title']."</td>";
				echo "<td>".$coupon['coupon_created_by']."</td>";
				echo "<td><a href='mailto:".$coupon['coupon_status']."'>".$coupon['email']."</a></td>";
				echo "<td>".$coupon['subscriber_id']."</td>";
*/
//echo "</tr>";


?>
<!--</table>-->

  <input type="text" name="textfield" value="<?php print $coupon['businessname']; ?>">
</td>
  </tr>
   <tr><td>&nbsp;</td></tr>
  <tr>
    <th scope="row">Contact Name</th>
    <td>&nbsp;</td>
    <td> <input type="text" name="textfield2" value="<?php print $coupon['contactname'];?>"></td>
  </tr>
   <tr><td>&nbsp;</td></tr>
  <tr>
    <th scope="row">Address</th>
    <td>&nbsp;</td>
    <td>  <textarea name="textarea" value="<?php print $coupon['address']; ?>"></textarea></td>
  </tr>
  <tr><td>&nbsp;</td></tr>
  <tr>
    <th scope="row">E Mail</th>
    <td>&nbsp;</td>
    <td> <input type="text" name="textfield3" value="<?php print $coupon['email']; }} ?>" size="50"></td>
  </tr>
   <tr><td>&nbsp;</td></tr>
  <tr>
    <th scope="row">Company Logo</th>
    <td width="9%" class="Bodytext"><div align="center">:</div></td>
    <td width="65%"><input type="file" name="btnLogoFile"><input type=button class=butn name=btn value="Preview" onClick="return DoPreview();"><br>                                  <BR>
                                  <img src="images/spacer.gif"></td>
  </tr>
   <tr><td>&nbsp;</td></tr>
  <tr>
    <th scope="row">&nbsp;</th>
    <td>&nbsp;</td>
    <td><input type="submit" name="submit" value="Submit Info"></td>
  </tr>
   <tr><td>&nbsp;</td></tr>
  <tr>
    <th scope="row">&nbsp;</th>
    <td>&nbsp;</td>
    <td>&nbsp; </td>
  </tr>
   <tr><td>&nbsp;</td></tr>
</table>
</form>
<?php
$var2 = microtime();
echo "<br>Elapsed Time: ".($var2 - $var1);
 ?>