Reloading A Frame On A Timer

Suppose I have two frames, as shown in the script below. One of the frames,
I would like to have reload every ten minutes or so. Hower, the frame I wish
to reload is a php script, which executes and creates a png image which gets
displayed directly to the browser frame (therefore, the image is NOT written
to the server itself, and the page that gets displayed in the frame I wish
to update is a png image mime type).

How can I amend my script in my page which holds the frameset (i.e. the
parent) such that only one particular frame is updated at a fixed interval?

<frameset rows="10%,90%>
<frame src="ggtab1a.php" name="main" scrolling="no" noresize
FRAMEBORDER=0 BORDER=0 FRAMESPACING=0 marginwidth="1"
marginheight="1">

<?php
echo "<frame src="reports/homepages/" . $username.".php" ";
?>

name="work1" FRAMEBORDER=0 BORDER=0 FRAMESPACING=0 marginwidth="0"