CBN_EDITCHANGE
idComboBox = LOWORD(wParam);
hwndComboBox = (HWND)lParam;
The CBN_EDITCHANGE notification message is sent after the user has taken an action that may have altered the text in the edit-control portion of a combo box. Unlike the CBN_EDITUPDATE notification message, this notification message is sent after Windows updates the screen. The parent window of the combo box 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 message does not occur if the combo box does not contain an edit control.
WM_COMMAND