Finding missing records

Finding missing records

I have a challenge and I am not really sure where to start with it.  I can't find any similar threads on here, can anyone help:

I have two forms, FormA and FormB.  Both forms have records that contain a field called Job_Number.  What I am trying to achieve is in FormA to find all unique Job_Number and then in FormB establish if any of the unique formA records do not have at least one corresponding Job_Number record within FormB.

Example:
Let's say that FormA had 10 records of which 8 are unique.  In FormB I want to know if there are at least 8 matching Job_Number records.

If NO, I want to return the COUNT of Records in FormA without a match in FormB and ideally, a list of the Job_Numbers in FormA that do not have a match.

Any ideas anyone?
Thanks