Problem with ClipCursor API to restrict the mouse within a window control using C# ?

[ck.kislay]

When I passed bounding area ( Location,height ,width )of a Window
control to the ClipCursor API it restrict the mouse in screen
coordinate ,Its fine because ClipCursor works on Screen coordinate. But
when I changed the bounding area (Location) to Screen coordinate then
pass to ClipCursor API then some time it works and some time it
doesn't work. Also how can unrestrict the mouse from ClipCursor?

Waiting for Reply,
Chandan Kumar