Forms accessing multiple tables?

Hi

I have a potential customer asking for help collecting information into a database as follows (the database doesnt exist yet, everything is from scractch)

Charity (Tax id, name , address)
Once a Charity is collected, the user can add an employee (email address, first, last)
Both charity and employee must be collected from visitors using forms

Then a visitor can enter a donation (location, employee email address, donation of cardboard in lbs)

How can I accomplish this?

In other words:
Can I have a form with drop down (charity) and have the charity itself be maintained by a visitor?

Any help is appretiated!