PhpDig.net - Change user-agent name

I have a website in english and french and I want to have 2 phpdig installation, one to search the french pages and one for the english pages.

I want to block access to the english pages to the french phpdig and vice versa in my robots.txt file.

For example my robots.txt would look like :

Code:

#phpdig for english pages

User-agent: PhpDig

Disallow: /fr/

#phpdig for french pages

User-agent: PhpDigFr

Disallow: /en/

I have read some post on how to change the user-agent name and I've changed the robot_functions.php and spider.php files without success.

Any help would be much appreciated.