C / C++ / MFC

int CALLBACK ListViewCompareProc(LPARAM lParam1,
                                 LPARAM lParam2,
                                 LPARAM lParamSort)
{
  int iResult = 0;
  
  int iClickedCol = int(lParamSort);
  
  if (0 <= iClickedCol && iClickedCol < 3) {
    NOTATIONINFO* nNot1=(NOTATIONINFO*) lParam1;        // item A to be compared
    NOTATIONINFO* nNot2=(NOTATIONINFO*) lParam2;        // with item B
  
    iResult = g_arOrders[iClickedCol] ?
              _tcscmp(nNot1->szEvent, nNot2->szEvent) : // forwards sorting
              _tcscmp(nNot2->szEvent, nNot1->szEvent);  // backwards sorting
  }
  
  return iResult;
}

...
  lvi.pszText = _T("0");
  listItemIndex = ListView_InsertItem(hLVWnd, &lvi);
...

int CALLBACK ListViewCompareProc(LPARAM lParam1,
                                 LPARAM lParam2,
                                 LPARAM lParamSort)
{
  int iResult = 0;
    
  int iClickedCol = int(lParamSort);
  
  if (0 <= iClickedCol && iClickedCol < 3) {
    NOTATIONINFO* nNot1=(NOTATIONINFO*) lParam1;        // item A to be compared
    NOTATIONINFO* nNot2=(NOTATIONINFO*) lParam2;        // with item B
  
// see your comparing fields:
    MessageBox(NULL,
               nNot1->szEvent,
               nNot2->szEvent,
               MB_OK);
  
    iResult = g_arOrders[iClickedCol] ?
              _tcscmp(nNot1->szEvent, nNot2->szEvent) : // forwards sorting
              _tcscmp(nNot2->szEvent, nNot1->szEvent);  // backwards sorting
  }
  
  return iResult;
}

NOTINFO* pInfo = new NOTINFO;
pInfo->nEpoch = ...;
// filling of pInfo->szDateTime and pInfo->szEvent
// setting pInfo as item param (not &pInfo)

NOTINFO* pInfo = (NOTINFO*) GetItemParam(i);
delete pInfo;

NOTINFO* pInfo = new NOTINFO;

...........
NOTATIONINFO *NotationList = new NOTATIONINFO;
.......
.......
lvi.Param =(LPARAM)NotationList; 
.......

for (int i = 0; i < Nnots; i++)
		{
			NOTATIONINFO         *NotationList      = (NOTATIONINFO*)GetItemParam(i);
			delete NotationList;
		}

...
case WM_DESTROY:
{
  LVITEM lvItem = {0};
  for (int i = 0; i < Nnots; i++) {
    lvItem.iItem = i;
    lvItem.mask  = LVIF_PARAM;
    ListView_GetItem(hwndList, &lvItem);
    NOTINFO* pInfo = (NOTINFO*) lvItem.lParam;
    delete pInfo;
  }
}
break;
...