An application sends an LB_SETITEMDATA message to set a 32-bit value associated with the specified item in a list box.
LB_SETITEMDATA wParam = (WPARAM) index; // item index lParam = (LPARAM) dwData; // value to associate with item
Windows 95: The wParam parameter is limited to 16-bit values.
This means list boxes cannot contain more than 32,767 items. Although the
number of items is restricted, the total size in bytes of the items in a
listbox is limited only by available memory.
If an error occurs, the return value is LB_ERR.
If the item is in an owner-drawn list box created without the LBS_HASSTRINGS style, this message replaces the 32-bit value contained in the lParam parameter of the LB_ADDSTRING or LB_INSERTSTRING message that added the item to the list box.