Using IFrame To Pull External Forms That Cannot Change

Order entry project. I am using an iFrame to pull external forms that I can not change. Once our employee enters in the information and submits I would like to redirect the existing window to a new page.

I've tried many variations of:
<script type='text/javascript'>
function iHistory() {
var hist=history.length;
if (hist>1){
parent.window.location = "orderentry.php";
}}
</script>

Since I have no control of the external form I have been using OnLoad() in the iFrame tag to call iHistory(). The script works great unless the browser history is >1 If possible, I would like to also setup like a 5 or 10 second delay so the employee can see the framed confirmation page before redirect. So the function needs to check current history.length, when that changes delay 5-10 seconds and redirect parent window to orderentry.php