Overlapping <DIV>

Hi,

Could someone please point me to the direction where I can find the script(s) for a DIV overlapping an HTML page that closes itself after x seconds?
What I'm trying to do is get div that serves as a loading screen which has a transparent SWF in it, and that div needs to overlap the contents of the HTML page to get an effect like when you load Adobe Reader- the lines that overlap the screen with shadow.
Any help would be GREATLY appreciated :)
Thanks!