htaccess RewriteRule - regexp problems

[dbrb2]

Hi - I'm having saome trouble with my htaccess redirect, and hoped someone could help:

I have a php page here:

http://bbarker.co.uk/animate/gpx.php

I am trying to ensure that anybody visiting this directory gets sent to this page automatically. However, I also want to ensure that if the request is as follows:

?file=something.json

(where something can be any string) Then they are not redirected, and the url parameter is kept. I'm sure I can do this with reqriteRule, but can't work out ho to specify a match on anything BUT a certain string...

Cheers,

Ben