javascript search; target main frame...

The following code is not mine and I can't remember for the life of me where I got it but I need help modifying it. What it does is takes a keyword from a form and searches the text on the page the script resides on and highlites any matches.

I want to put the script in a frame at the top of the page and have it search the text in the main frame but I dont know how to modify it so that it will do this. Any help will be much appreciated.

[CODE]
<script language="JavaScript">

var NS4 = (document.layers);
var IE4 = (document.all);

var win = window;
var n = 0;

function findInPage(str) {

var txt, i, found;

if (str == "")
return false;

if (NS4) {

if (!win.find(str))
while(win.find(str, false, true))
n++;
else
n++;

if (n == 0)
alert("Not found.");
}

if (IE4) {
txt = win.document.body.createTextRange();

for (i = 0; i <= n && (found = txt.findText(str)) != false; i++) {
txt.moveStart("character", 1);
txt.moveEnd("textedit");
}

if (found) {
txt.moveStart("character", -1);
txt.findText(str);
txt.select();
txt.scrollIntoView();
n++;
}

else {
if (n > 0) {
n = 0;
findInPage(str);
}

else
alert("Not found.");
}
}

return false;
}

</script>