I want to have an on-line form for customers which will create a case. I believe that if a customer is logged in it will attached the case to the customers account but if not it will either attach it to a dedicated account "Anonymous Customer" or if you expose the fields name address email etc it will make a new account.

This is horrid for customers who are logged in because they only want to see the drop-down (Quotations/Returns/Accounts/etc) and the free form text box.

Is there a way for the forms to know if a customer is logged in and therefore ask just the nature of the case and give them the free form box and if they are not logged in to then ask all the relevant questions such as name, address,phone, email.