怎么让VC子窗口变成椭圆形?

VB的例子：
调用的是API函数
Attribute VB_Name = "Module1"
Public Declare Function CreatePolygonRgn _
Lib "gdi32" _
( _
lpPoint As POINTAPI, ByVal nCount As Long, _
ByVal nPolyFillMode As Long _
) As Long
Public Type POINTAPI
x As Long
y As Long
End Type
'------------------------------------------------
'以上为声明CreatePolygonRgn函数和它需要的POINTAPI类型

Public Declare Function SetWindowRgn _
Lib "user32" _
( _
ByVal hWnd As Long, ByVal hRgn As Long, _
ByVal bRedraw As Boolean _
) As Long
Public Const ALTERNATE = 1
'------------------------------------------
''以上为声明SetWindowRgn函数和它需要的常量

Public Sub Poly(f As Form)
Dim hdc1 As Long
Dim rec(37) As POINTAPI
rec(0).x = 102
rec(0).y = 11
rec(1).x = 12
rec(1).y = 102
rec(2).x = 11