I'm having a bit of a JavaScript issue. I want to open a JavaScript prompt() window from the parent window, then open a new (popup) window (the contents of this window are not under my control ...

It's been a while since I've done anything like this but it seems to me that you could open up the new window and set the reference to the new window to a variable. Then you should be able to call ...

A server-side request could be initiated when the user clicks a Submit button, for example, or clicks on a link, or calls JavaScript’s form.submit, window.open, or window.showModalDialog methods ...