Adding a String to a list box in WinAPI

Hey!
I'm having a bit of trouble simply adding a string to an empty listbox in C++ WinAPI. The Listbox is initialised as follows:

#
hwndObjList = CreateWindowEx(0, TEXT("LISTBOX"), TEXT(""),
                WS_CHILD | WS_VISIBLE | WS_BORDER| LBS_STANDARD|LBS_HASSTRINGS, 20, 185, 170, 95, hwndObjectives,
                (HMENU)  IDOBJLIST , NULL, NULL);

I've tried adding a string as follows, but to no avail: (I have only included relevant lines)

string szObjectivesArray[noObjectives][2];
string* buffer = &szObjectivesArray[0][0];

for (int Counter = 0; Counter < noObjectives; Counter++)
        {
            GetFirstIndex(file, ((Counter + 1) * 2) - 1, szObjectivesArray[Counter][0]);
            GetSecondIndex(file, ((Counter + 1) * 2) - 1, szObjectivesArray[Counter][1]);
        }
SendMessage(hwndObjList, LB_ADDSTRING, NULL, (LPARAM)buffer);

I've tried one or two other methods of adding a string, but I can't see why this isn't working. the output is just an empty list box
(this code is included under a WM_CREATE message under the hwndObjectives window which contains the list box)