Excel form design

I need a form designing (must be very user friendly) which includes lookups to another worksheet which in turn populate dropdowns and subsequent dropdowns. The remainder of form will then need to pre populate based upon the drop down selections with some fields the user can change if required - this will finally include check boxes which need some code applying so that users can change up to 2 of the check boxes but no more than 2. Ideally the form then would need to submit via email.