This LINK targets and changes the lower two frames.  
This is the code for the Frameset:

<html>
<head>
<title>Frameset</title>
</head>

<frameset rows="80%,*" borders="1/2">
   <frame src="frame1.html" name="fr1">
   <frameset cols="50%,*">
     <frame src="ltyellow.html" name="fr2">
     <frame src="ltyellow.html" name="fr3">
   <frameset>
<frameset>

</html>

  This is the code for the top frame (frame1.html)
which contains the javascript and the code that targets frames 2 and 3:

<html>
<head>
<title>Frame1</title>
</head>

<script language="JavaScript">
<!-- Hiding
   function loadtwo(page2, page3) {
     parent.fr2.location.href=page2;
     parent.fr3.location.href=page3;
}
// -->
</script>

</head>
<body bgcolor="#ffffff">

<a name="top"> </a>

This <a href="#top" onClick="loadtwo('lowleft.html','lowright.html')">LINK</a>
targets and changes the lower two frames.

</body>
</html>