XSSI check a querystring = a file that exists?

[matc]

Hello,

I'm working on switching all our .htaccess files into XSSI expressions (geared for Apache 2) but need to check if a submitted querystring value corresponds to an existing file.

Its an interesting problem and I'm not sure how to recreate this in XSSI, can anybody help?

Basically the QS comes in as id=0134 and I want to check that the $value of id is a file that exists in a certain location. Its either something like this or doing an id look up of some 4300+ different values for each call made to the page... which is slight crippling.

A example of the location and what it has to check on would be:
/directory/over/here/${value}.shtml - (yep without escaping any char to read easier)

Can anyone see a good way of doing this in XSSI or would this have to remain as a htaccess -f flag.

Many thanks for any help offered,
matc

[matc]

I found some help with coming up with a solution here: [vmsbox.cjb.net...]
This page gives some very good pointers on using SSI's as well as how to detect a files existance (Section 4.9.1).