static extern IntPtr CreateRectRgn(int nLeftRect, int nTopRect, int nRightRect, int nBottomRect);

Private Shared Function CreateRectRgn(ByVal nLeftRect As Integer, ByVal nTopRect As Integer, ByVal nRightRect As Integer, ByVal nBottomRect As Integer) As IntPtr

        static extern IntPtr CreateRectRgn(int nLeftRect, int nTopRect, int nRightRect,

                FillRgn(wDc, CreateRectRgn(0,0,mx,my), brush);

        static extern IntPtr CreateRectRgn(int nLeftRect, int nTopRect, int nRightRect,

                FillRgn(wDc, CreateRectRgn(0,0,mx,my), brush);

        static extern IntPtr CreateRectRgn(int nLeftRect, int nTopRect, int nRightRect,

                FillRgn(wDc, CreateRectRgn(0,0,mx,my), brush);

IntPtr hRegion = CreateRectRgn(left, top, right, bottom);