Not sure if this is the best way to do this, but you could accomplish what you are trying to do with the following.
on the page you want them to "click here" start a session. Lets say for our case
session_start();
$ok_to_download = 1;
session_register("ok_to_download");
than on your download page have something like...
if(!isset($ok_to_download)){
$ok_to_download = 0;
}
if($ok_to_download == 1){
//continue with download
}
else {
//redirect to verify page
header("location: http://www.yourwebpage/your/page.html");
}
You can refine this to better suite your needs, just the first way that popped into my head.
Cheers
John