need to redirect and rewrite subdir of one site to another server

Hi,

I'm operating a website on an external hosting ("www.mydomain.tld" and "mydomain.tld" are both pointed to the external IP provided by the webhosting, the DNS server is local and fully customizable). Locally, there is another server that hosts another machine of the domain, lets name it "trouble.mydomain.tld". Recently, i been asked to, without moving the content, make a link between a new subdir on "www.mydomain.tld" and the local machine, to work like this:

www.mydomain.tld/trouble ----> trouble.mydomain.tld
___(external hosting)_______link_____(locally operated)

BUT, they need to keep the first direction ALWAYS visible to visitors, so even when the content is hosted locally at the "trouble.mydomain.tld" machine, visitors should see "trouble.mydomain.tld/index.php" (or any other content and subdirs) as "www.mydomain.tld/trouble/index.php" on their web browsers.

Is this possible? could you please give me a hint on how to achieve this?

Thanks in advance.

 

This should give you the idea: http://httpd.apache.org/docs/2.2/rewrite/rewrite_guide.html