Draws the part of a parent control that is covered by a partially-transparent or alpha-blended child control
_WinAPI_DrawThemeParentBackground ( $hWnd, $hDC [, $tRECT = 0] )
|$hWnd||Handle of the child control.|
|$hDC||Handle to the child control's DC.|
|$tRECT||[optional] $tagRECT structure that defines the area, in the child window's coordinates, to be drawn.|
|Failure:||0 and sets the @error flag to non-zero, @extended flag may contain the HRESULT error code.|
Search DrawThemeParentBackground in MSDN Library.