You can do this easily with a querystring that passes the URL to load as follows:

First, add JavaScript to the header of index1.htm:
(note that test is the name/id of your iframe element)

<script type="text/javascript">
function loadIframe()
{
var urlStr;
urlStr = location.search .slice(1);
window.frames.t est.location = urlStr;
}
</script>...