change the browser identity

My company needs to be able to test client from different company who
visit our web page. For testing purposes, we are looking for a
solution where we could easily emulate client coming different
countries. I was wondering if squid proxy server can easily be
configure to do this. Does any one know? Simply put, we need to be
able to fake the identity of the browser to a different language,
etc...

Thanks in advance.
.