BCGControlBar Pro for MFC
UINT BCGM_ON_MOVETOTABGROUP

Notifies the parent frame that an MDI child window has been moved from one tabbed group to another.

Parameters
wParama handle to tabbed window (CBCGPTabWnd) from which the MDI child window has been removed.
lParama handle to tabbed window (CBCGPTabWnd) to which the MDI child window has been inserted.
Returns
The return value is ignored.

The message is sent to the main frame window when an MDI child window has been moved from one tabbed group to another.