The TB_ADDBUTTONS message adds one or more buttons to a toolbar.
TB_ADDBUTTONS wParam = (WPARAM) (UINT) uNumButtons; lParam = (LPARAM) (LPTBBUTTON) lpButtons;
Returns TRUE if successful or FALSE otherwise.
If the toolbar was created by using the CreateWindowEx function, you must send the TB_BUTTONSTRUCTSIZE message to the toolbar before sending TB_ADDBUTTONS.