APEX

Trying out APEX 3.1 and I'm in an environment where the users access the app via a security proxy. This renames the server, so, for example, for my flash charts to work, I have to change the region source to replace #HOST# with https://www.securityproxy.com/myapp/
It seems like this same problem is happening with the javascript on the interactive reports; I get a syntax error when I try to do anything on an interactive report that goes through the security proxies, but not if I am accessing the server directly (which is not allowed).
Is there something I can do about this? Should I be somehow substituting the #HOST# value in my app? I tried using the application definition substitution strings (substitution string = HOST and substitution value = https://www.securityproxy.com/myapp/), but this didn't work for the flash charts (I didn't try for interactive reports).
Thanks, -w