Well here you find an example and tutorials about how to develop such software. In this example it is already a little chat. I don't know, whether you are able to read this as it is written in german.
http://www.delphi-library.de/viewtopic.php?p=336933
But if you have to make this at school, then it won't help you anything if you just copy a piece of code somewhere. If you don't understand what you are doing your teacher will of course realize that it is not from you...