look up form more then one field

Hi all i am new to Adobe Sing and have little programing experience but I can normally get by with some basic scripts. 

I want to create a look up for price based on more than one field. I have drop down to select vehicle type, then its size and have a calculated field for the price.

Right now I have used conditional fields that don’t only show up depending on vehicle type, for example first drop down field has Boat and jet ski. If jet ski a field a jetski_size becomes visible, and for boats boats_size becomes visible. I can get the form to lookup form a single field but how can I do it for both?