htaccess virtual subdomain with 2 parameters

How can I turn one or more virtual directory into parameters

[cartuchos]

Hello all,
I have been trying to get htaccess handle virtual subdomains. I would like it to do the following:
if I visit
[mydomain.com...] it redirects to [mydomain.com...]

and if I visit

[mydomain.com...] it redirects to [mydomain.com...]

Can anyone please tell me how this is done, the examples I have seen on the forums didn't seem to work for me,

thanks so much in advance!

[jdMorgan]

This thread [webmasterworld.com] from our library might be a good place to start.

Jim