BCGControlBar Pro for MFC
virtual BOOL CBCGPGridCtrl::CanDropColumnToColumnChooser ( int  nColumn) const

Tells whether a column can be dropped on the Column Chooser.

Should return TRUE, if the specified column can be dropped during drag-and-drop operations; otherwise FALSE.
nColumnSpecifies the zero-based index of column.

Override this function and return FALSE to prevent hiding of the specified column by dropping it on the Column Chooser.

By default this method returns TRUE. Use this method in conjunction with CanHideColumn().