1) Yes it is, you have to select which point is the Destination though.
2) passing the session through the URL Variable like this does not make sense.
the whole point of using session variables is that once they are set they are available to all of the pages in your site. you don't need to pass the session using the URL.
instead you can reference the session on the index.php page just be using the code i gave.
one point:
this code:
if("" == "") {
$_SESSION["ServiceID"] = "".$_GET['ID'] ."";
}
will set the session on page load, regardless of whether the ID url variable has a value or not.
you may want to change the trigger for the set session value code to use the ID url variable.