Car Rental Access Database (small and very easy)

I have a school homework in microsoft access and i need help doing it. Teacher asked me for designing a basic car rental database with login security form. I have problem when an order needs to rent the same car in the same date period. So i don't know how to prevent data conflicts. it's very easy and basicly designed for beginners. this url contain the assignment word file: <[login to view URL]> ## Deliverables Every thig related is in the attachment works for word 2003 ## Platform Should be made for access 2007 and run on windows vista and 7 Try not to use advanced formulas Don't use VBA If Possible You can use macros(simpile) Should use Reports, Forms Feel free to make it your own way but please don't use very advanced methods as possible Thanks for help