The EN_HSCROLL notification message is sent when the user clicks an edit control's horizontal scroll bar. The parent window of the edit control receives this notification message through the WM_COMMAND message. The parent window is notified before the screen is updated.
EN_HSCROLL
idEditCtrl = (int) LOWORD(wParam); // identifier of edit control
hwndEditCtrl = (HWND) lParam; // handle of edit control
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Requires version 1.0 or later.
Header: Declared in winuser.h.
Edit Controls Overview, Edit Control Messages, EN_VSCROLL, WM_COMMAND