BCGControlBar Pro for MFC
HWND CBCGPToolBar::GetHwndLastFocus ( ) const

Returns a handle to window that previously had the input focus.

A handle to window other than CBCGPBaseToolBar - derived control, which had the input focus. It can be NULL.

When a CBCGPToolBar control receives the input focus, it stores a handle to a window that lost the focus in order to be able to restore it later.