How to add hidden value to dropdown items and show the calculated total in Paypal?

I've been trying to use the Form Calculation widget to work out the cost of an order that a customer would put through out form.

We have a wide range of options for the customer to select and each option may add or subtract from the final total.

Is there any way that I can add a hidden value to each option in a drop down list that a widget like Form Calculation will pick up and be able to use?  I don't mind having the value on display but because our products are named by their size, "8x8" for example, it really messes with Form Calculation, so a defined value for each option would be handy rather than relying on what the option is called...  Is this possible?  Maybe there is a better widget than Form Calculation for us to use?

Also, is it possible for Jot Form to take the total that Form Calculation comes up with, and send it to Paypal to make a payment of that total?