Should be possible, but it isn't Plus..
1) Check the options: 
  a) Autologin
  b) Save password
Create a new task with the task scheduler which starts MSN Messenger 
Logging out is a bit harder, but you can try a cool named "Pskill"  (http://www.sysinternals.com/Utilities/PsKill.html)
Should work!
If not, try "AutoIT" combined with the Task Planner 

 AutoIT is a scripting language which can create macro's..