CB_DELETESTRING
wParam = (WPARAM) index; /* item to delete */
lParam = 0; /* 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-draw 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.
CB_RESETCONTENT, WM_DELETEITEM