not sure if i completely follow you..
you have a popup window that displays 1 picture and a <-- and a --> button.
When you click on <-- or --> you want the picture that is already displayed to change to the prev or next pic dependant on what button they hit?
To do this you want to reload the page with new picture based on the URL that is passed to it from when the user clicked the button?
so the window looks something like this:
----------------
|....My pic.....|
|....My pic.....|
|....My pic.....|
| <-- --> |
---------------
if you hit, <--, reload the page with popupwin.htm?ID=5
if you hit, -->, reload the page with popupwin.htm?ID=7
so in your <body> of the popup window you will want to put
<script language="javascript:drawThePic();"></script>
and then in the <head> put:
function drawThePic()
{
PicID = document.URL.slice(document.URL.indexOf("?")+1);
document.writeln('<IMG SRC="'+PicID+'.jpg">');
}
You would get the back and next links by doing something like:
thePicNum = document.URL.document.URL.slice(document.URL.indexOf("?")+1).substring(0,1);
backPic = thePicNum-1;
if(backPic <1) backPic = 15;
nextPic = thePicNum+1;
if(nextPic >15) nextPic = 1;
backLink = "popupwin.htm?ID="+backPic;
nextNum = "popupwin.htm?ID="+nextPic;
then you can use javascript to write the links:
document.writeln('<a href="'+backLink+'">');
document.writeln('<a href="'+nextLink+'">');
I hope that isn't too confusing... it was just off the top of my head