How to create a price look up form?

Is there a form where the customer can select a size, then select a quantity and the form looks up the price?  There would be no calculation, the form would pull the price from a hidden table.  I would need multiple sizes and multiple quantities from which the customer would choose.

I'm afraid that this will not be possible to achieve, you cannot select options already set in a table and then place them into the payment field. 

I think this will be possible to achieve, without using calculations, using conditions, but it will required to have a lot of conditions, one for each possible case and then insert the needed amount in the payment field. 

Here is a guide about conditions that will help you with this: Smart-Forms-Using-Conditional-Logic

Otherwise you will need to use calculations to get the amount into the payment field, but would be good to provide us the details about how you want this to be calculated, we should be able to help.