int SetWindowRgn(
HWND hWnd, // handle to window whose window region is to be set
HRGN hRgn, // handle to region
BOOL bRedraw // window redraw flag
);

Information From Win32.hlp

With FindWindow, I can fill in the first parameter.

* At Form.load()
Declare Integer FindWindow In Win32API;
STRING @lpClassName, STRING @lpWindowName

lctitletext = Thisform.Caption
lnhWnd = FindWindow(0, @lctitletext)

Declare Integer SetWindowRgn In Win32API;
Integer hWnd, Integer hRgn, Bool bRedraw

---

Then, If I want to resize to polygram window, or circle window?!
What should I pass at middle parameter?! ?_?

Actually, how it make the window into a Non-rectanglar shape?!