I got this thing cooking the way I wanted  to,
but I have 1 small problem. I click  on the ImageButton
which opens a new window and reads the x, y coords
from Session vars then invokes the Handler to get me
the detail image. Great, works fine. Image returns and
loads in an Image control in the new window, 3 seconds
later the new window closes. Now, if I want to click the
ImageButton again, the window opens and I see the
image I saw last time. If I click the same spot a second
time I then get what I wanted. I wonder if the browser
is caching the image, because each time I ask for this
image it has the same file name.

I'm thinking about changing it so that when I click on
the ImageButton it goes and gets the new image and I save
the original image on the client-side. Then I'll show the new
image in the ImageButton and after 3 seconds replace  this
new image with the original by using a 3 second setTimeout
activated by a click event  attribute added to the ImageButton.

I don't think my Handler code could be duplicated with
Javascript. Check the attachment.