Here's the basic outline of what you will need to do:
When you VC++ program starts, you will need to connect to the arduino over the COM port (user configurable would be a good thing)
The VC++ program displays the UI which consists of a "Next" button. When the user clicks on it, the program sends a command over the COM port to the arduino
The arduino receives the command and toggles the control lines to make your indexer do what you want.
repeat as needed.