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.

Notification messages are sent from a control window (edit or listtbox) to
its parent window when certain events happen to the control.

 CBN_DBLCLK
 CBN_EDITCHANGE
 CBN_ERRSPACE
 CBN_KILLFOCUS
 CBN_SELCHANGE
 CBN_SETFOCUS
 EN_CHANGE
 EN_HSCROLL
 EN_KILLFOCUS
 EN_SETFOCUS
 EN_VSCROLL
 LBN_DBLCLK
 LBN_ERRSPACE
 LBN_SELCHANGE