CBN_SELENDOK
idComboBox = LOWORD(wParam);
hwndComboBox = (HWND)lParam;
The CBN_SELENDOK notification message is sent when the user selects an item and then either presses the ENTER key or clicks the DOWN ARROW key to hide the list box of a combo box. This notification message is sent before the CBN_CLOSEUP notification message to indicate that the user's selection should be considered valid.
idComboBox
Value of low word of wParam. Specifies the combo-box ID.
hwndComboBox
Value of lParam. Specifies the combo-box window handle.
The CBN_SELENDOK or CBN_SELENDCANCEL notification message is sent even if the CBN_CLOSEUP notification message is not sent (as in the case of a combo box with the CBS_SIMPLE style).
CBN_SELENDCANCEL, WM_COMMAND