<iframe>Question about them</iframe>

I have a question about Iframes. I was wondering how one would go about loading a new page into an i frame when a link is clicked on the site. I have a flash navigation bar and when a user clicks on the navbar, i would like it to load the specified page into the Iframe instead of loading an entirly new page. If that doesnt make much sense, let me know and I will try to explain better.