This program makes the ellipse big enough to include pieces of the form's borders so you can resize the form. The program rebuilds the ellipse whenever the form is resized.

Private Sub Form_Resize()
Dim rgn As Long
Dim wid As Single
Dim hgt As Single

    If WindowState = vbMinimized Then Exit Sub

    ' Create the elliptical region.
    wid = ScaleX(Width, vbTwips, vbPixels)
    hgt = ScaleY(Height, vbTwips, vbPixels)
    rgn = CreateEllipticRgn(0, 0, wid, hgt)

    ' Restrict the window to the region.
    SetWindowRgn hWnd, rgn, True
    DeleteObject rgn

    Command1.Move _
        (ScaleWidth - Command1.Width) / 2, _
        (ScaleHeight - Command1.Height) / 2
End Sub