One login for 2 separate installs

[ziola1039]

I am looking at doing multiples installs of CMS Made Simple at like company1.mydomain.com and company2.mydomain.com. I was wondering how I could put a login on the homepage at www.mydomain.com where that if company1 logged in they would get redirected to their private content at company1.mydomain.com or if company2 logged in on www.mydomain.com they would get directed to their private content that I have at company2.mydomain.com. In other words I was wondering how I could have 1 login that might direct users to separate installs of CMS Made Simple. Thanks!