Backend with multiple URIs

Hi,

I have been using nginx for the past 5 years, and use it for a lot of projects. But I am unable to set this certain configuration up.

I have a site that has a set amount of sub-uri's pointing to the same backend and I need to make sure that only a specific set of files are accessible from that backend.

example:
I need to be able to say that
/bluewidget/
/greenwidget/
/redwidget/
etc.. 240 uris later
/blackwidget/

point to a specific backend with proxy pass.

But, for all of those uri specifications I only want to allow access to
index.html
purchase.html
confirm.html

and nothing else.

So even though "admin.html" is accessible from the backend I want to prevent access (i.e. show a 404 or better yet, make the nginx engine look for a filesystem /xxwidget/admin.html


This could also be described the other way around.
1) I want to only allow a specific amount of files to be available through the proxy pass.
index\.(.*)
purchase\.(.*)
etc..
and use that access definition for X amount of sub uri's (same will be applicable for all since URIs are used as a parameter in the coding engine)

Is this possible with nginx ?

Thank you
Oli