Is it possible to pass information to Siebel which can be used during the session?

Hello Experts

I am trying to find out if there is a way to pass information to Siebel while logging in which can be captured at Application Load event and be utilized. The scenario is that the customer wants to enter Position Id at the login page and pass it into Siebel  while logging on, and that position should be set as the active position on login (provided the user is associated to that position).

Any pointers will be appreciated.

Thanks