An application sends a LB_INSERTSTRING message to insert a string into the list box. Unlike the LB_ADDSTRING message, the LB_INSERTSTRING message does not cause a list with the CBS_SORT style to be sorted.
The LB_INSERTSTRING message may be used as either a wide-character message (where text arguments must use Unicode) or an ANSI message (where text arguments must use characters from the Windows 3.x character set installed).
wParam
Specifies the zero-based index of the position to insert the string. If this parameter is -1, the string is added to the end of the list. The high-order word of wParam is not used.
lParam
Points to the null-terminated string that is to be inserted. If the list was created with an owner-draw style but without the LBS_HASSTRINGS style, the value of the lParam parameter is stored rather then the string it would otherwise point to.
The return value is the index of the position at which the string was inserted. The return value is LB_ERR if an error occurs; the return value is LB_ERRSPACE if insufficient space is available to store the new string.
LB_ADDSTRING