Add div to webpage from Flash

I’m making an expandable ad and it is working perfectly except for one flaw. The expanded part of the ad is currently hard coded into the index files div. Like below…

<div style=“width: 518px; height: 0px;visibility:hidden” id=“windowcontent”>
<object classid=“clsid:d27cdb6e-ae6d-11cf-96b8-444553540000”
codebase=“http://fpdownload.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=9,0,0,0
width=“738” height=“500” id=“Popup” align=“middle”>
<param name=“allowScriptAccess” value=“sameDomain” />
<param name=“movie” value=“bannerads/Popup.swf” />
<param name=“wmode” value=“transparent” />
<param name=“scale” value=“exactfit” />
<param name=“quality” value=“high” />
<param name=“bgcolor” value="#333" />
<param name=“Popup” value=“true” />
<embed src=“bannerads/Popup.swf” name=“Popup” allowScriptAccess=“sameDomain”
type=“application/x-shockwave-flash” pluginspage=“http://www.adobe.com/go/getflashplayer
quality=“high” bgcolor=“FFFFFF” width=“738” height=“500” wmode=“transparent” align=“middle” />
</object>
</div>

I would like to be able to have my index page keep this part…

<div style=“width: 518px; height: 0px;visibility:hidden” id=“windowcontent”>

</div>

and from the flash file when I rollover the swf I would like it to add whatever swf I tell it to add to the “windowcontent” div…