Calculation issue

Hello

I set up a website for online applying of trademarks

http://www.ra-plutte.de/markenanmeldung
PW: npl2012

In step 2 of the multi-page-form people can choose from up tp 45 classes. Each class costs 100 € in general, while up to three classes always costs 300,00 € (so 1, 2 or 3 classes = 300,00 €, while 5 classes would for example be 500,00 €).

What I want to do is add a value of 100,00 € to each of the 45 classes and show the final sum in step 4 of the form, depending on how many classes the user checked in step 2. What I don't want is the single-value to be seen on the pre-submission page, so it should be hidden.

I was thinking of a hidden calculation field plus conditional logic depending if the sum is above or less then 300,00 €. Unfortunately it didn't work :(

Any suggestions on how to get there?

Thanks for your response Chris. Maybe I am not able to answer your question right, because I am unsure about the best way of how to implement the fee issue.

First: The DPMA fee calculator field shall be shown on the page you linked at this position. I want people to be aware of the class costs underneath the lawyer fee before reaching the order summary.

What I need help with is the calculation method as described above. I have tried adding a value of 100 € to each of the 45 classes in step 2 with additional hidden fields + conditional logic. Apart from lower website performance (form got quite big) the main problem is that hidden field values are shown in the order summary of gf_pre_submission, which is not wanted. These values would have to be hidden in the order summary. Is this possible so all hidden field values are really totally hidden and only used for background calculation? Or do you recommend using the "Value" option inside the checkbox fields as an easier way? If yes, how do I get a clean order summary? In my tests the label (i.e. "Klasse 01") was not shown anymore but its value (= "100,00€").

Second problem is that the DPMA fee calculator shows 100 € for 1 selected class and 200 € for 2 selected classes. This is wrong, because the basic DPMA fee is 300 €. I tried to work with calculation + conditional field, but so far did not find a proper function to display this one correct. Do you see a way?

PS. My website text is amazingly well translated, seriously ;)