EN_UPDATE
The EN_UPDATE notification message is sent when an edit control is about to screen altered text. This notification is sent after the control has formatted the text but before it screens the text. This makes it possible to alter the window size, if necessary. The control's parent window receives this notification message through a WM_COMMAND message.
wParam
Specifies the identifier of the edit control.
lParam
Specifies the handle of the edit control in the low-order word, and specifies the EN_UPDATE notification message in the high-order word.