Private Sub Form_Resize()
Const RGN_DIFF = 4

Dim outer_rgn As Long
Dim inner_rgn As Long
Dim combined_rgn As Long
Dim wid As Single
Dim hgt As Single
Dim border_width As Single
Dim title_height As Single

    If WindowState = vbMinimized Then Exit Sub
    
    With picBox
        ' set the picture box to be measured in pixels
        .ScaleMode = vbPixels
        
        ' Create the regions.
        wid = .Width
        hgt = .Height
        outer_rgn = CreateRectRgn(0, 0, wid, hgt)
        
        border_width = (wid - .ScaleWidth) / 2
        title_height = hgt - border_width - .ScaleHeight
        inner_rgn = CreateEllipticRgn( _
            border_width + .ScaleWidth * 0.1, _
            title_height + .ScaleHeight * 0.1, _
            .ScaleWidth * 0.9, .ScaleHeight * 0.9)
    
        ' Subtract the inner region from the outer.
        combined_rgn = CreateRectRgn(0, 0, 0, 0)
        CombineRgn combined_rgn, outer_rgn, _
            inner_rgn, RGN_DIFF
        
        ' Restrict the picture box to the region.
        SetWindowRgn .hWnd, combined_rgn, True
    End With
End Sub