SetWindowRgn for a button

Is it true that SetWindowRgn is not applicapable for buttons and also another controls of window?

It's just because I cannot set a region for the button on my dialog window in OnInitDialog, This is the code:

Code:

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    CWnd *pBtn = GetDlgItem( IDC_BUTTON1 );
    CRect rc;
    pBtn->GetWindowRect( &rc );
    HRGN hRgn = CreateEllipticRgn( 0, 0, rc.Width(), rc.Height() );
    pBtn->SetWindowRgn( hRgn, TRUE );

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For the top level window (that is for dialog window) this code works well, but for a button - nothing changes.

ModifyStyle(0, WS_CLIPCHILDREN | WS_CLIPSIBLINGS , SWP_FRAMECHANGED);
But do not expect the end of your trouble. Button drawing is complex; it draws itself with three colors, not to mention default button frame.