Hi Alex: Your sensitivity to avoid offending a guest is notable. I think are serveral ways to approach this situation. First I would acknowledge their great knowledge and experience and express your appreciation that they are willing to speak to your class. KEY: I would then give them a short list of the topics you are currently covering (or want to covered), and politely ask if they would try to integrate these into their presentation. I would also add that they're welcome to speak about anything else they feel is relative and the students might benefit from. You might indicate that your students have had a particularly difficult time with these topics and to have another expert reinforce it, it would also help to validate your emphasis on the topics. Most speakers will not mind getting a heads up on what the teachers wants them to speak abot. Also, you can indicate (whether true or not) that your students will be tested on this material so you want to make sure it's covered. With all that, you shouldn't too much difficulty. Good luck! Regards, Barry