I'd like the next functionality

I must have my websites at:

/var/www/vhosts/example.org

example.org has got the following structure:

httpdocs

logs

subdomains

After i access the http://example.org i'd like the documentroot to become

/var/www/vhosts/example.org/httpdocs

after i hit around the browser http://test.example.org the documentroot to become:

/var/www/vhosts/example.org/subdomains/test/httpdocs

I believe this may be completed with mod_vhost_alias however i could no get it done.

Basically put this:

UseCanonicalName Off
<VirtualHost *:80>
    VirtualDocumentRoot /var/www/vhosts/%0/httpdocs/
</VirtualHost>

for that above example document root is /var/www/vhosts/example.org/httpdocs (example.org) and /var/www/vhosts/test.example.org/httpdocs (test.example.org)

I'd like something similar to:

UseCanonicalName Off
<VirtualHost *:80>
    if not subdomain:
        VirtualDocumentRoot /var/www/vhosts/%0/httpdocs/
    else:
        VirtualDocumentRoot /var/www/vhosts/%domain/subdomains/%subdomain/httpdocs/
</VirtualHost>

How do i get it done?