CB_DELETESTRING
wParam = (WPARAM) index; /* item to delete */
lParam = 0L; /* not used, must be zero */
An application sends a CB_DELETESTRING message to delete a string in the list box of a combo box.
index
Value of wParam. Specifies the zero-based index of the string to delete.
The return value is a count of the strings remaining in the list. The return value is CB_ERR if the index parameter specifies an index greater than the number of items in the list.
If the combo box was created with an owner-drawn style but without the CBS_HASSTRINGS style, a WM_DELETEITEM message is sent to the owner of the combo box so that the application can free any additional data associated with the item.
This example deletes the first string in a combo box:
DWORD dwRemaining;
dwRemaining = SendDlgItemMessage(hdlg, ID_MYCOMBOBOX,
CB_DELETESTRING, 0, 0L);