CBN_CLOSEUP
idComboBox = LOWORD(wParam);
hwndComboBox = (HWND)lParam;
The CBN_CLOSEUP notification message is sent when the list box of a combo box is hidden. The control's parent window receives this notification message through a WM_COMMAND message.
idComboBox
Value of low word of wParam. Specifies the combo-box ID.
hwndComboBox
Value of lParam. Specifies the combo-box window handle.
This notification message is not sent to a combo box that has the CBS_SIMPLE style.
An application should not make assumptions about the order in which notifications are sent. In particular, a CBN_SELCHANGE notification may occur either before or after a CBN_CLOSEUP notification.
CBN_DROPDOWN, CBN_SELCHANGE, WM_COMMAND