Gravity Forms Add On calculation -> Multiply possible?

Hi there, I've been browsing documentation, the support forum and FAQ's for hours but can't seem to find a way to get my form to work properly...

I bought Gravity Form Add On to use with Woocommerce.
What I would like to have is the following option (for a rental situation):
The customer not only selects the number of items he/she wants, they also need to select the number of days they want to use it. When they select 2 days, the base price per item should automatically be multiplied with 2. When they select 5 days, it should multiply with 5, etc...

We figured this would be possible with this plugin, is it? Maybe in the form of a calculation? Tried a lot but I can't seem to find a way to configure this. Unfortunately the (limited) documentation on this add-on doesn't make it clear to me either.

A test product can be found here: http://fietsverhuurwormer.nl/dev/product/test-fiets-calculatie/ When needed I can provide a support login.

(I'm also willing to pay someone to get this done for me! Please let me know your price if you can make this work for me. Thanks in advance!)

Any help would be very much appreciated!

Hi Chris, thanks for your reply! The example you gave does indeed have the same requirements.

One question about that though: Do you make the options per product in that solution?
Because what we would like to create is a calculation that can be used with every product, not making several options for each and every product.

I wasn't sure if my question was easy to realise, maybe some of you clever guys knew how to do this right away. But if I get it right, it's not a simple question to answer, so I'll probably have to go to the job boards?

Thanks anyway for the advices!

Thanks for the advice and your time Chris,
I'm going to post it on the job board!