How do I use other information from a look-up record?

How do I use other information from a look-up record?

Once I have identified a related record through a look-up field, 

ex for billing out a service whose price is based on 1) the square feet of the job, and 2) utilizing a specific formula which is priced per sq. foot.

I have created the table that gathers the information for each job and I can use a look-up field to specify which formula should be used,  but I would also like to have the price per square foot of the formula (which is in the formula's record) and then multiply that number by the square feet of the job (which is in the job record)