lostdreamer - 12:14 pm on Sep 17, 2012 (gmt 0)
Welcome to this forum :)
It sounds like an easy one:
<iframe NAME="my_iframe" src="somepage.html"></iframe>
<a href="some_other_page.html" TARGET="my_iframe"> Switch to other page</a>
Just make sure your iframe has a unique name, and use that name as the target value in your links.