If you are using plain old windows ( not a wraaper library like MFC or QT), then you send
messages to the listbox.
There are a lot of messages you can send to a list box - one of them is LB_GETTEXT. The listbox will return the text associated with the currently selected item.
See here: http://msdn.microsoft.com/en-us/library/bb761313(VS.85).aspx