The TCM_INSERTITEM message inserts a new tab in a tab control. You can send this message explicitly or by using the TabCtrl_InsertItem macro.
TCM_INSERTITEM wParam = (WPARAM) (int) iItem; \\index of the new tab lParam = (LPARAM) (const TC_ITEM FAR*) pitem; \\pointer to struct specifying tab attributes
Returns the index of the new tab if successful or - 1 otherwise.