Each message which is sent to a window procedure has two data items which
serve as arguments to that message. The two items are a word-long item,
wParam, and  double-word-long item, lParam. The lParam argument is
ocassionally subdivided into two word-long parameters. These word can be
extracted using the LOWORD(lParam) and the HIWORD(lParam) macros.

 CB_ADDSTRING
 CB_DELETESTRING
 CB_DIR
 CB_FINDSTRING
 CB_GETCOUNT
 CB_GETCURSEL
 CB_GETEDITSEL
 CB_GETLBTEXT
 CB_GETLBTEXTLEN
 CB_INSERTSTRING
 CB_LIMITTEXT
 CB_RESETCONTENT
 CB_SELECTSTRING
 CB_SETCURSEL
 CB_SETEDITSEL
 CB_SHOWDROPDOWN