I need some help with Access Log Files, but don't know if this feasible...

I have 3 pointed sub-domains running on top of my main.

Is there a way (through .htaccess ?) to have the requested files URL that are mentioned in the access logs reflect the specific sub-domains or main domain where those files are located?

i.e. :
instead of: - - [02/Jan/2011:04:52:20 -0500] "GET /robots.txt HTTP/1.1" 200 614 "-" "Mozilla/5.0 (compatible; bingbot/2.0; +http://www.bing.com/bingbot.htm)"

I would like to see something like: - - [02/Jan/2011:04:52:20 -0500] "GET sub-domain-2/robots.txt HTTP/1.1" 200 614 "-" "Mozilla/5.0 (compatible; bingbot/2.0; +http://www.bing.com/bingbot.htm)"