Create a login form linked to another wordpress site in network

Hey! I am wondering if it is possible to create a login form on, that is linked to in a network.
With other words, I want it to be possible to login from my "main" site, to my "member" site without entering the "member" site.
I think it should work because it is not two different wordpress installations, it is a network!

Tnx for answer,
Regards, Marcus