How to run two clients with different login credentials?

[sharpMouse]

Problem:

I run first client.
I run second client.
I get the disconnect with reason "already logged in".

So I have to log out in first client and login manually to another account.

Need:

Login to both clients automatically (without using multiboxing software).

Questions:

1. May be there are some .bat files to do this?
2. May be some command line options or .wtf file settings which may help?
3. Any other semi-easy way like run and send several keystrokes?
4. If double login is impossible, how to run one client with login and second client without the try to login?