web.xml error page relative host

How do I specify a error-page in my web.xml which redirects to a relative page not hosted on the application server?

For example

Web Server (Host A) forwards to Application Server (Host B). Application Server fails and uses the error page in web.xml to return a page that exists on the Web Server (Host A).

In web.xml I don't want to hardcode the Host A server name and should therefore be relative, ie /error/errorpage.html

but I don't see how to achieve that using the "location" field in the errorpage.