This message is sent by a list box with the LBS_WANTKEYBOARDINPUT style to its owner in response to a WM_CHAR message.
wParam
Contains the current caret position in its high-order word and the value of the key which the user pressed in the low-order word.
lParam
Contains the window handle of the list box.
The return value specifies the action which the application performed in response to the message. A return value of -2 indicates that the application handled all apsects of selecting the item and wants no further action by the list box. A return value of -1 indicates that the list box should perform the default action in response to the key stroke. A return value of zero or greater specifies the index of an item in the list box and indicates that the list box should perform the default action for the key stroke on the given item.
WM_CHAR