Session Problem ASP.net

Hi to all
I have been facing problem with Session in ASP.net Application.

I have 2 applications Called MainAPp, ChildApp.

In MainApp i have Link to Open Seperate Window to Naviate Child Application Form.

I have created Sesion("userID") in MainApp. I want to Use this Sesion("userID") in Child Application. How do i achive this???

But i don't want to use it by CookieLess.

Cheers
Buddu