An application sends an EM_SETMODIFY message to set or clear the modification flag for an edit control. The modification flag indicates whether the text within the edit control has been modified. It is automatically set whenever the user changes the text. An EM_GETMODIFY message can be sent to retrieve the value of the modification flag.
EM_SETMODIFY wParam = (WPARAM) (UINT) fModified; // modification flag lParam = 0; // not used; must be zero
This message does not return a value.
In a rich edit control, objects created without the REO_DYNAMICSIZE flag will lock in their extents when the modify flag is set to FALSE.