Quick and messy code, but it works. You'll need to style the DIV elements though.

PHP Code: 
<?php
if (isset($_GET['link']))
{
  
$link trim($_GET['link']);
}
?>

<script type="text/javascript"><!--
function ReplaceContentInContainer(id,content) {
var container = document.getElementById(id);
container.innerHTML = content;
}
//--></script>


<div 
   id="example3div" 
   style="border-style:dotted; 
          padding:10px; 
          font-size:24px; 
          width:200px; 
          text-align:center;">

</div>

<script type="text/javascript"><!--
var containerID = "example3div";
var number = 10; //change to no. of secs to wait
var timerID = setInterval("CountdownTimer()",1000);
function CountdownTimer() {
if(number > 1) {
    number--;
    ReplaceContentInContainer(containerID,number);
    }
else {
    clearInterval(timerID);
    ReplaceContentInContainer(containerID,'<a href="<?php echo $link?>"><?php echo $link?></a>');
    }
}
//--></script>
Usage:
- Copy the code, save it to a file. Save file as .php (anyfile.php).
- Link in the format
Code: 
http://example.com/file.php?link=http://filehost.com/file.ext
- Edit the code to change the countdown timer (check the comment for the variable to edit) and to style the DIV element.