vertical scrolls

Hello Everyone,

I am still stuck on vertical scrolls as I was last week. If someone knows 
the answer to the follwoing question, please mail me.

I need to know the  properties of a vertical scroll. How can I
tie it with the length of a window? I want the scroll to handle 
dynamically increasing length of my window? Also, does this change the way 
in which the window is declared?


Please consider this as urgent and reply as soon as possible

Thanks a lot
Atin.