dynamic content with php only?

[the.janitor]

I am trying to add external content using "openPage()"-method and escaped ruby code:

jsFunction="openPage('center','Upload','<%= escape_javascript(url_for({ :action => "upload"})) %>','Upload')"

I get: "Message from DHTMLSuite.dynamicContent
The ajax request for /admin/upload failed"
althougth the URL is correct.

Is it possible to include external Non-PHP/JS-files?
Thanks

[the.janitor]