Before using Scrollbar.UseWinBorder
you first have to enable border scrollers
for the parent window by setting the appropriate window class attributes. For
example, if you want to put the scrollbar into the bottom window border, you
would have to set the Window.UseBottomBorderScroller attribute first.
See Window class for details.
Also note that there obviously can only be two scrollbars in the window border: One on the left or right, and one in the bottom window border.
The following values are recognized by this attribute:
Left
Right
Bottom