Keyboard control over iRobot

I am currently working on a project for a physics class and we are trying to connect our Roomba robot(iRobot) to the keyboard using the command: [keyPresses , elapsedTime] = RobotHardKeyBoard(CommPort) We have tried multiple inputs into each variable but there is always an error. If someone could help provide an example of what variables are defined and how we would go about it, it would be great.