Build a dynamic form based on user input
If I understand well, one user need to enter informations for X persons who has to attend to your future meeting right?

To do it, I think the better way is to create a content type and use CCK with multiple field. If you need a group of fields, you can install CCK 3.X that include multiple_group module. It's a module very useful that allow you create a group of fields and the user can multiple it at infinite or as you wish.