Calculating "total" of product measured in feet?

Hi,

I am trying to create an online calculator, where I can get the client to calculate their required office space.

It's broken down into three sections;

1) the user selects the type of space i.e reception / office
2) the user selects the size of the space i.e small 140 sq ft / medium 250 sq ft/ large 420 sq ft
3) summary of their requirements i.e 1 x reception (M) 250 sq, 2 x offices (S) 140 sq ft
Total Size = XXXX sq feet
Submit

Basically, I need to add everything together.

As there is no price, I am unsure as to how to work out the total and how to go about it to manually show up the added items onto the summary section?

I do realise this is a bit hard to explain and possibly understand, so if required, I can add a pic as to what I am trying to do.

Thank you very much in advanced, please be gentle, this is my first post!

Regards,

G.

Carl,

Thank you for your reply. I was hoping that the pricing fields could be modified as such to accomodate for my requirements, however, as you have stated, they can't.

This was one of the main reasons for purchasing the developer license.

When you say this "In order to do this you could only do it as a customization by writing custom jQuery to calculate values of certain fields and update the value of the total field" do you mean within Gravity forms or as something completely different?

Thank you very much for your time,

G.