This macro returns the number of items in the List Box.

#define INCL_WINWINDOWMGR /* Or use INCL_WIN, INCL_PM, */
#include <os2.h>

HWND    hwndLbox;   /*  Listbox handle. */
LONG    lRetNumIt;  /*  Number of items in the list box. */

lRetNumIt = WinQueryLboxCount(hwndLbox);