Title: make a Hole in a form?
procedure TForm1.Button1Click(Sender: TObject);
var
region1, region2: hrgn;
begin
region1 := CreateRectRgn(0, 0, Width, Height);
region2 := CreateEllipticRgn(30, 30, 200, 200);
CombineRgn(region1, region1, region2, RGN_DIFF);
SetWindowRgn(Handle, region1, True);
end;