Auto fit iframe to content?

I am working on a site where I am using iframes, Each asp file opend in the iframe having its own length and my iframe height is fixed.

When you call any external file into that iframe, then you have to set iframe height.

Now I want to set page height as per external page height so that no scroll appears for the iframe, i want it to just extend its self to the hight of the page it is showing.

And, my problem is that my contents are dynamic page height will vary page to page.

Is there any way to set iframe to change height automatically for each page loaded in it ?.