Routing Fluid form to specific Individual based on data input of another field

Hi,

I am working on creating a fluid form that needs to be routed to specific individual based on data input of another field, for e.g. route to an Instructor based on Class number data input on the form. Any idea how can that be achieved? I know we can route to a userlist in Approval Process Setup by defining a criteria. But how do I send it to specific individual? I can create a SQL definition (query below) Userlist with a parameter but how do I bind that parameter with the user input class number?

SELECT oprid
FROM psoprdefn