EN_CHANGE
idEditControl = LOWORD(wParam);
hwndEditControl = (HWND)lParam;
The EN_CHANGE notification message is sent when the user has taken an action that may have altered text in an edit control. Unlike the EN_UPDATE notification message, this notification message is sent after Windows updates the display. The control's parent window receives this notification message through a WM_COMMAND message.
idEditControl
Value of low word of wParam. Specifies the edit-control ID.
hwndEditControl
Value of lParam. Specifies the edit-control window handle.
WM_COMMAND