Where to find (and change) {vb:raw url} ?

[thehawkVB]

I'm on a reverse proxy system and when I delete a post I end up with:

<input type="hidden" name="url" value="/~websitename/forum/showthread.php ... etc

I want to omit the "/~websitename/forum/" part.

The change would not break "Other functions and mods", would it? hmmm

Of course I'm open to more elegant solutions, if any.

--------------- Added [DATE]1305919982[/DATE] at [TIME]1305919982[/TIME] ---------------

Here are more details:

My website is located at : http://www.mydomain.com
Forum, on a different server, is located at : http://www.mydomain.com/forum

The forum loads correctly and works correctly via a ReWrite Proxy rule on the first server.

The only problem is that when I delete a post, in the "Physically remove" screen, the hidden field <input type="hidden" name="url" has this value:
/~websitename/forum/showthread.php/etc. etc.

Of course I have no rule in the first server to tackle "/~websitename/forum/". I can add it, but I believe removing that part would work better.