[Zope] Suggestions on getting proper URL in ZPT?

Hi all, I've got a few page templates that need to contain references to Python scripts that are in parallel directories to them. How can I make this work so that no matter where the page template is used, it is always able to call the Python script? One way I thought of was simply obtaining the url of the page template, relative to the server root, and working from there. But I don't know how to find the URL of the page template. Any sort of suggestions would be appreciated. Alec Munro