Designing a multi-parameter search

I have a pretty complex issue to share with you. I'm working on a financial system, which will provide its customers the option to make a search by more than one parameter.

I'm trying to keep the search bar as simple as possible, and give-up on the "advanced search" option. The problem is that it is very complicated to make it clear for the user that the "enter" button is not taking him/her straight to search, it is just adding a new parameter for the search. How would you make it easy to understand?