I did it like this :

<form name =YourName>
<iframe src="Mypage.asp?MyVar=' & text1.value '&Myvar2=' &text2.value">
</iframe>
</form>

Or instead you can do in javascript:
YourIFRAME.Navigate("Mypage.asp?MyVar=' & text1.value ")

In this case your asp page shows up inside of frame.
But don't forget , NN does not know IFRAME !

Another tricky part, is to send values from Mypage.asp
to parent page, you have to use something like :

When child form loads, do it in body onload:

parent.form.element.value=iframeForm.element.value,
It will not work other way around!