How to get cells to auto-fill data from another Excel File?

Hi

I am new to using Excel. I have set up some VERY basic files. I teach several classes and have an excel file for key contact data on students and their families. Each class has it's own set of data. However, I have many students who are in multiple classes. I don't want to have to manually key in the same data on each file. Is there a way I can make all the files automatically recognize the data from other files so I don't have to keep repeating it? The same idea as when I type in an email address into the "To:" field on email it starts to recognize my choices and I can select from those given. This would save me a ton of time!

I hope I explained this in a way that conveys what I mean.

Thanks in Advance.

Access? I know nothing of it. Will check it out.

I have an after school enrichment coordination business. I contract with instructors to bring classes to elementary schools. I teach the art and science classes for my program. I am in Petaluma.

Off I go to check out Access.

thanks

Apparently, I do not have Access. I keep getting an Access denied message.